TOPIC: COMPUTER SECURITY
An unseen arsenal: How web developers can use specialised tools to build better websites
4th March 2026
Modern web development takes place within an ecosystem of tools so precisely suited to individual tasks that they often go unnoticed by anyone outside the profession. These utilities, spanning performance analysers, security checkers and colour palette generators, form the backbone of a workflow that must balance speed, security and visual consistency. For an industry where user experience and technical efficiency are inseparable priorities, such tools are far from optional luxuries.
Performance Testing and Page Speed Analysis
The first hurdle most developers encounter is performance measurement, and several tools have established themselves as essential in this space. GTmetrix, Google PageSpeed Insights and WebPageTest each draw on Google's open-source Lighthouse framework to varying degrees, though each approaches the task differently.
A performance grade alongside separate scores for page speed and structural quality is what GTmetrix produces for any URL submitted to it. It measures Core Web Vitals, including Largest Contentful Paint (LCP), Total Blocking Time (TBT) and Cumulative Layout Shift (CLS), which are the same metrics Google uses as ranking signals in search. The tool can run tests from multiple global server locations and simulates a real browser loading your page, producing a waterfall chart and a video replay of the load process, so developers can identify precisely which elements are causing delays.
Maintained directly by Google, PageSpeed Insights analyses pages against both laboratory data generated through Lighthouse and real-world field data drawn from the Chrome User Experience Report (CrUX). It provides separate performance scores for mobile and desktop, which is significant given that Google confirmed page speed as a ranking factor for mobile searches in July 2018. Both GTmetrix and PageSpeed Insights go well beyond raw figures, mapping out a prioritised list of optimisations so that developers can address the most impactful issues first.
A different position in the toolkit is occupied by WebPageTest, originally created by Patrick Meenan and open-sourced in 2008, and acquired by Catchpoint in 2020. Rather than returning a simple score, it runs tests from a choice of locations across the globe using real browsers at actual connection speeds, and produces detailed waterfall charts that break down every individual network request. This makes it the tool of choice when the question is not just how fast a page is, but precisely why a particular element is slow.
One of the longer-established names in website speed testing, Pingdom offers a free tool that remains widely used for its accessible reporting. Tests can be run from seven global server locations, and results are presented in four sections: a waterfall breakdown, a performance grade, a page analysis and a historical record of previous tests. The page analysis breaks down asset sizes by domain and content type, which is useful for comparing the weight of CDN-served assets against those served directly. Pingdom is based on the YSlow open-source project and does not currently measure the Core Web Vitals metrics that Google uses as ranking signals, so it is best treated as a quick and readable first pass rather than a definitive audit.
Security and Infrastructure Diagnostics
Performance alone cannot sustain a trustworthy website, as a misconfigured certificate, an insecure resource or a flagged IP address can each undermine user confidence and search visibility. One of the most frustrating post-migration problems is the disappearance of the HTTPS padlock despite an SSL certificate being in place, and Why No Padlock? exists specifically to address it. The cause is almost always mixed content, where a page served over HTTPS loads at least one resource (an image, a script or a stylesheet) over plain HTTP. Why No Padlock? scans any HTTPS URL and returns a list of every insecure resource found, along with the HTML element responsible, making it straightforward to trace and resolve the problem. Google has used HTTPS as a ranking signal since 2014, so unresolved mixed content issues carry an SEO cost as well as a security one.
For traffic-level threats, AbuseIPDB operates as a community-maintained IP blacklist. Managed by Marathon Studios Inc., the project allows system administrators and webmasters to report IP addresses involved in malicious behaviour, including hacking attempts, spam campaigns, DDoS attacks and phishing, and to check any IP address against the database before acting on traffic from it. A free API is available for integration with server tools such as Fail2Ban, enabling automatic reporting and real-time checks.
Bot traffic and automated form submissions are a persistent nuisance for any site that accepts user input, and hCaptcha addresses this by presenting challenges that are straightforward for human visitors but reliably difficult for automated scripts. Operated by Intuition Machines, it positions itself as a privacy-focused alternative to reCAPTCHA, collecting minimal data and retaining no personally identifiable information beyond what is necessary to complete a challenge. It is compliant with GDPR, CCPA and several other international privacy frameworks, and holds both ISO 27001 and SOC 2 Type II certifications. A free tier is available, with a Pro plan covering 100,000 evaluations per month, and an Enterprise tier offering additional controls including data localisation and zero-PII processing modes.
Red Sift offers two distinct products that address different aspects of infrastructure security, both relevant to the day-to-day operation of a website. Red Sift OnDMARC automates the configuration and monitoring of DMARC, SPF, DKIM, BIMI and MTA-STS, which are the protocols that collectively prevent attackers from sending spoofed emails that appear to originate from a legitimate domain. This is the basis for most phishing and business email compromise (BEC) attacks, and OnDMARC guides teams to full enforcement typically within six to eight weeks. Red Sift Certificates Lite addresses a separate but equally critical concern, monitoring SSL/TLS certificates for upcoming expiry and alerting administrators seven days ahead of time. It is free for up to 250 certificates and has been formally recommended by Let's Encrypt as its preferred monitoring service, following the retirement of Let's Encrypt's own expiry notification emails. The product was built on the foundation of Hardenize, which Red Sift acquired in 2022, a company founded by Ivan Ristić, creator of SSL Labs.
Colour Management and Visual Design
A website's visual coherence depends heavily on colour consistency, and the distance between a palette sketched on paper and one that functions in code can be significant. With over two million active users, Coolors is a fast and intuitive palette generator built around a simple interaction: pressing the space bar produces a new five-colour palette derived from colour theory algorithms. The platform includes an accessibility checker that calculates contrast ratios against WCAG standards and a colour extractor that derives palettes from uploaded photographs. It also offers interoperability with Figma, Adobe Creative Suite and the Chrome browser. A free tier is available, with a Pro plan at approximately $3 per month for unlimited saving and export options.
A quite different approach is taken by Colormind, which uses a deep learning model based on Generative Adversarial Networks (GANs) to generate harmonious colour schemes. The model is trained on datasets drawn from photographs, films, popular art and website designs, and is updated daily with fresh material. A particularly useful feature allows users to preview how a generated palette would look applied to a website layout, which is a more direct test of practicality than viewing swatches in isolation. A REST API is available for personal and non-commercial use. For converting between colour formats, tools such as Color-Hex, RGBtoHex and the WebFX Hex to RGB converter bridge the gap between design decisions and code implementation, translating colour values in both directions between the hexadecimal and RGB formats that CSS requires.
Optimisation and Code Utilities
Lean, efficient code is a direct contributor to load speed, and unused CSS is a surprisingly common source of unnecessary page weight that PurifyCSS Online addresses by scanning a website's HTML and JavaScript source against its stylesheets to identify selectors that are never used. CSS frameworks such as Bootstrap or Tailwind ship with many utility classes, and most websites use only a small fraction of them. Removing the unused rules can reduce stylesheet file size substantially, which in turn shortens the time a browser spends processing styles before rendering a page. The online version requires no build pipeline or command-line tools, making it accessible to developers at any workflow stage.
Image compression is equally important, as unoptimised images are among the most common causes of slow load times. ImageCompressor handles JPEG, PNG, WebP, GIF and SVG files in the browser, applying lossy or lossless algorithms with adjustable quality settings to reduce file sizes without visible degradation, and processes everything locally, which means that no images are uploaded to an external server. Contact forms and directory listings on websites are a persistent target for spam harvesters, and Email Obfuscator encodes email addresses into a format that is readable by browsers but opaque to most automated scrapers, generating both a plain HTML entity version and a JavaScript-dependent alternative for stronger protection.
For websites that publish mathematical or scientific content, QuickLaTeX provides a practical solution to embedding equations in web pages without a local LaTeX installation. Authors write standard LaTeX expressions directly in their content, and the service renders them as high-quality images that are cached and returned via URL for embedding. Its companion WordPress plugin, WP QuickLaTeX, handles this process automatically within the editor, supporting inline formulas, numbered displayed equations and TikZ graphics.
Server Response and Infrastructure Monitoring
Infrastructure performance sits beneath the layer that most visitors ever see, yet it determines how quickly any content reaches a browser at all, and the Time to First Byte (TTFB) is the metric that captures this most directly. It measures the interval between a browser sending an HTTP request and receiving the first byte of data from the server, and ByteCheck exists solely to measure it. This metric captures the combined effect of DNS resolution time, TCP connection time, SSL negotiation time and server processing time. Google considers a TTFB of 200ms or below to be good, and Byte Check breaks the total down into each constituent step, so developers can identify precisely where delays are occurring. Slow TTFB is often a server-side issue, such as inadequate caching, an overloaded database or a lack of a content delivery network (CDN).
Analytics and Content Evaluation
The final layer of tooling concerns understanding what content a site serves and how it performs in context. Dandelion is a natural language processing API developed by SpazioDati that can extract entities, classify text and analyse the semantic content of web pages, which has applications in content tagging, SEO auditing and editorial quality control. A free tier, covering up to 1,000 API units per day, is available without a credit card, making it accessible for developers who need semantic analysis at low to moderate volume.
Quiet Workhorses of the Web
Individually, each of these tools addresses a specific and well-defined problem. Taken together, they form a coherent toolkit that covers the full lifecycle of a web project, from initial performance diagnosis through to deployment of a secure, efficiently coded and visually consistent site. They do not replace professional judgement but extend it, handling time-consuming checks and conversions that would otherwise consume the attention needed for more complex work. As websites grow in complexity and user expectations continue to rise, familiarity with this kind of specialist tooling becomes a practical necessity rather than an optional extra.
Security is a behaviour, not a tick-box
11th February 2026
Cybersecurity is often discussed in terms of controls and compliance, yet most security failures begin and end with human action. A growing body of practice now places behaviour at the centre, drawing on psychology, neuroscience, history and economics to help people replace old habits with new ones. George Finney's Well Aware Security have built its entire approach around this idea, reframing awareness training as a driver of measurable outcomes rather than a box-ticking exercise, with coaches helping colleagues identify and build upon their existing strengths. It is also personal by design, using insights about how minds work to guide change one habit at a time rather than expecting wholesale transformation overnight.
This emphasis on behaviour is not a dismissal of technical skill so much as a reminder that skill alone is insufficient. Security is not a competency you either possess or lack; it is a behaviour that can be learned, reinforced and normalised. As social beings, we have always gathered for mutual protection, meaning the desire to contribute to collective security is already present in most people. Turning that impulse into daily action requires structure and patience, and it thrives when a supportive culture takes root.
Culture matters because norms are powerful. In a team where speed and convenience consistently override prudence, individuals who try to do the right thing can feel isolated. Conversely, when an organisation embraces cybersecurity at every level, a small group can create sufficient leverage to shift practices across the whole business. Research has found that organisations with below-average culture ratings are significantly more likely to experience a data breach than their peers, and controls alone cannot close that gap when behaviours are pulling in the opposite direction.
This is why advocates of habit-based security speak of changing one step at a time, celebrating progress and maintaining momentum. The same thinking underpins practical measures at home and at work, where small changes in how devices and data are managed can reduce risk materially without making technology difficult to use.
Network-Wide Blocking with Pi-hole
One concrete example of this approach is network-wide blocking of advertising and tracking domains using a DNS sinkhole. Pi-hole has become popular because it protects all devices on a network without requiring any client-side software to be installed on each one. It runs lightly on Linux, blocks content outside the browser (such as within mobile apps and smart TVs) and can optionally act as a DHCP server so that new devices are protected automatically upon joining the network.
Pi-hole's web dashboard surfaces insights into DNS queries and blocked domains, while a command-line interface and an API offer further control for those who need it. It caches DNS responses to speed up everyday browsing, supports both IPv4 and IPv6, and scales from small households to environments handling very high query volumes. The project is free and open source, sustained by donations and volunteer effort.
Choosing What to Block
Selecting what to block is a point at which behaviour and technology intersect. It is tempting to load every available blocklist in the hope of maximum protection, but as Avoid the Hack notes in its detailed guide to Pi-hole blocklists, more is not always better. Many lists draw from common sources, so stacking them can add redundancy without improving coverage and may increase false positives (instances where legitimate sites are mistakenly blocked).
The most effective approach begins by considering what you want to block and why, then balancing that against the requirements of your devices and services. Blocking every Microsoft domain, for instance, could disrupt operating system updates or break websites that rely on Azure. Likewise, blacklisting all domains belonging to a streaming or gaming platform may render apps unusable. Aggressive configurations are possible, but they work best when paired with careful allow-listing of domains essential to your services. Allow lists require ongoing upkeep as services move or change, so they are not a one-off exercise.
Recommended Blocklists
A practical starting point is the well-maintained Steven Black unified hosts file, which consolidates several reputable sources and many users find sufficient straight away. From there, curated collections help tailor coverage further. EasyList provides a widely trusted foundation for blocking advertising and integrates with browser extensions such as uBlock Origin, while its companion list EasyPrivacy can add stronger tracking protection at the cost of occasional breakage on certain sites.
Hagezi maintains a comprehensive set of DNS blocklists, including "multi" variants of different sizes and aggression levels, built from numerous sources. Selecting one of the multi variants is usually preferable to layering many individual category lists, which can reintroduce the overlap you were trying to avoid. Firebog organises its lists by risk: green entries carry a lower risk of causing breakage, while blue entries are more aggressive, giving you the option to mix and match according to your comfort level.
Some projects bundle many sources into a single combination list. OISD is one such option, with its Basic variant focusing mainly on advertisements, Full extending to malware, scams, phishing, telemetry and tracking, and a separate NSFW set covering adult content. OISD updates roughly every 24 hours and is comprehensive enough that many users would not need additional lists. The trade-off is placing a significant degree of trust in a single maintainer and limiting the ability to assign different rule sets to different device groups within Pi-hole, so it is worth weighing convenience against flexibility before committing.
The Blocklist Project organises themed lists covering advertising, tracking, malware, phishing, fraud and social media domains, and these work with both Pi-hole and AdGuard Home. The project completed a full rebuild of its underlying infrastructure, replacing an inconsistent mix of scripts with a properly tested Python pipeline, automated validation on pull requests and a cleaner build process.
Existing list URLs are unchanged, so anyone already using the project's lists need not reconfigure anything. That said, the broader principle holds regardless of which project you use: blocklists can become outdated if not actively maintained, reducing their effectiveness over time.
Using Regular Expressions
For more granular control, Pi-hole supports regular expressions to match domain patterns. Regex entries are powerful and can be applied both to block and to allow traffic, but they reward specificity. Broad patterns risk false positives that break legitimate services, so community-maintained regex recommendations are a safer starting point than writing everything from scratch. Pi-hole's own documentation explains how expressions are evaluated in detail. Used judiciously, regex rules extend what list-based blocking can achieve without turning maintenance into an ongoing burden.
Installing Pi-hole
Installation is straightforward. Pi-hole can be deployed in a Linux container or directly on a supported operating system using an automated installer that asks a handful of questions and configures everything in under ten minutes. Once running, you point clients to use it as their DNS resolver, either by setting DHCP options on your router, so devices adopt it automatically, or by updating network settings on each device individually. Pairing Pi-hole with a VPN extends ad blocking to mobile devices when away from home, so limited data plans go further by not downloading unwanted content. Day-to-day management is handled via the web interface, where you can add domains to block or allow lists, review query logs, view long-term statistics and audit entries, with privacy modes that can be tuned to your environment.
Device-Level Adjustments
Network filtering is one layer in a defence-in-depth approach, and a few small device-level changes can reduce friction without sacrificing safety. Bitdefender's Safepay, for example, is designed to isolate banking and shopping sessions within a hardened browser environment. If its prompts become intrusive, you can turn off notifications by opening the Bitdefender interface, selecting Privacy, then Safepay settings, and toggling off both Safepay notifications and the option to use a VPN with Safepay. Bookmarked sites can still auto-launch Safepay unless you also disable the automatic-opening option. Even with notifications suppressed, you can start Safepay manually from the dashboard whenever you want the additional protection.
On Windows, unwanted prompts from Microsoft Edge about setting it as the default browser can be handled without resorting to arcane steps. The Windows Club covers the full range of methods available. Dismissing the banner by clicking "Not now" several times usually prevents it from reappearing, though a browser update or reset may bring the message back. Advanced users can disable the recommendations via edge://flags, or apply a registry policy under HKEY_CURRENT_USERSoftwarePoliciesMicrosoftEdge by setting DefaultBrowserSettingEnabled to 0. In older environments such as Windows 7, a Group Policy setting exists to stop Edge checking whether it is the default browser. These changes should be made with care, particularly in managed environments where administrators enforce default application associations across the estate.
Knowing What Your Devices Reveal
Awareness also begins with understanding what your devices reveal to the wider internet. Services like WhatIsMyIP.com display your public IP address, the approximate location derived from it and your internet service provider. For most home users, a public IP address is dynamic rather than fixed, meaning it can change when a router restarts or when an ISP reallocates addresses; on mobile networks it may change more frequently still as devices move between towers and routing systems.
Such tools also provide lookups for DNS and WHOIS information, and they explain the difference between public and private addressing. Complementary checks from WhatIsMyBrowser.com summarise your browser version, whether JavaScript and cookies are enabled, and whether known trackers or ad blockers are detected. Sharing that information with support teams can make troubleshooting considerably faster, since it quickly narrows down where problems are likely to sit.
Protecting Your Accounts
Checking for Breached Credentials
Account security is another area where habits do most of the heavy lifting. Checking whether your email address appears in known data breaches via Have I Been Pwned helps you decide when to change passwords or enable stronger protections. The service, created by security researcher Troy Hunt, tracks close to a thousand breached websites and over 17.5 billion compromised accounts, and offers notifications as well as a searchable dataset. Finding your address in a breach does not mean your account has been taken over, but it does mean you should avoid reusing passwords and should enable two-factor authentication wherever it is available.
Two-Factor Authentication
Authenticator apps provide time-based codes that attackers cannot guess, even when armed with a reused password. Aegis Authenticator is a free, open-source option for Android that stores your tokens in an encrypted vault with optional biometric unlock. It offers a clean interface with multiple themes, supports icons for quick identification and allows import and export from a wide range of other apps. Backups can be automatic, and you remain in full control, since the app works entirely offline without advertisements or tracking.
For users who prefer cloud backup and multi-device synchronisation, Authy from Twilio offers a popular alternative that pairs straightforward setup with secure backup and support for using tokens across more than one device. Both approaches strengthen accounts significantly, and the choice often comes down to whether you value local control above all else or prefer the convenience of synchronisation.
Password Management
Strong, unique passwords remain essential even alongside two-factor authentication. KeePassXC is a cross-platform password manager for Windows, macOS and Linux that keeps your credentials in an encrypted database stored wherever you choose, rather than on a vendor's servers. It is free and open source under the GPLv3 licence, and its development process is publicly visible on GitHub.
The project has undergone rigorous external scrutiny. On the 17th of November 2025, KeePassXC version 2.7.9 was awarded a Security Visa by the French National Cybersecurity Agency (ANSSI) under its First-level Security Certification (CSPN) programme, with report number ANSSI-CSPN-2025/16. The certification is valid for three years and is recognised in France and by the German Federal Office for Information Security. More recent releases such as version 2.7.11 focus on bug fixes and usability improvements, including import enhancements, better password-generation feedback and refinements to browser integration. Because data are stored locally, you can place the database in a private or shared cloud folder if you wish to sync between devices, while encryption remains entirely under your control.
Secure Email with Tuta
Email is a frequent target for attackers and a common source of data leakage, so the choice of client can make a meaningful difference. Tuta provides open-source desktop applications for Linux, Windows and macOS that bring its end-to-end encrypted mail and calendar to the desktop with features that go beyond the web interface. The clients are signed so that updates can be verified independently, and Tuta publishes its public key, so users can confirm signatures themselves.
There is a particular focus on Linux, with support for major distributions including Ubuntu, Debian, Fedora, Arch Linux, openSUSE and Linux Mint. Deep operating-system integration enables conveniences such as opening files as attachments directly from context menus on Windows via MAPI, setting Tuta as the default mail handler, using the system's secret storage and applying multi-language spell-checking. Hardware key support via U2F is available across all desktop clients, and offline mode means previously indexed emails, calendars and contacts remain accessible without an internet connection.
Tuta does not support IMAP because downloading and storing messages unencrypted on devices would undermine its end-to-end encryption model. Instead, features such as import and export are built directly into the clients; paid plans including Legend and Unlimited currently include email import that encrypts messages locally before uploading them. The applications are built on Electron to maintain feature parity across platforms, and Tuta offers the desktop clients free to all users to ensure that core security benefits are not gated behind a subscription.
Bringing Culture and Tooling Together
These individual strands reinforce one another when combined. A network-wide blocker reduces exposure to malvertising and tracking while nudging everyone in a household or office towards safer defaults. Small device-level settings cut noise without removing protection, which helps people maintain good habits because security becomes less intrusive. Visibility tools demystify what the internet can see and how browsers behave, which builds confidence. Password managers and authenticator apps make strong credentials and second factors the norm rather than the exception, and a secure email client protects communications by default.
None of these steps requires perfection, and each can be introduced one at a time. The key is to focus on outcomes, think like a coach and make security personal, so that habits take root and last.
There is no single fix that will stop every attack. One approach that does help is consistent behaviour supported by thoughtful choices of software and services. Start with one change that removes friction while adding protection, then build from there. Over time, those choices shape a culture in which people feel they have a genuine role in keeping themselves and their organisations safe, and the technology they rely upon reflects that commitment.
OWASP Top 10 for Large Language Model Applications
21st January 2024
OWASP stands for Open Web Application Security Project, and it is an online community dedicated to web application security. They are well known for their Top 10 Web Application Security Risks and late last year, they added a Top 10 for
Large Language Model (LLM) Applications.
Given that large language models made quite a splash last year, this was not before time. ChatGPT gained a lot of attention (OpenAI also has had DALL-E for generation of images for quite a while now), there are many others with Anthropic Claude and Perplexity also being mentioned more widely.
Figuring out what to do with any of these is not as easy as one might think. For someone more used to working with computer code, using natural language requests is quite a shift when you no longer have documentation that tells what can and what cannot be done. It is little wonder that prompt engineering has emerged as a way to deal with this.
Others have been plugging in LLM capability into chatbots and other applications, so security concerns have come to light, so far, I have not heard anything about a major security incident, but some are thinking already about how to deal with AI-suggested code that others already are using more and more.
Given all that, here is OWASP's summary of their Top 10 for LLM Applications. This is a subject that is sure to draw more and more interest with the increasing presence of artificial intelligence in our everyday working and no-working lives.
LLM01: Prompt Injection
This manipulates an LLM through crafty inputs, causing unintended actions by the LLM. Direct injections overwrite system prompts, while indirect ones manipulate inputs from external sources.
LLM02: Insecure Output Handling
This vulnerability occurs when an LLM output is accepted without scrutiny, exposing backend systems. Misuse may lead to severe consequences such as Cross-Site Scripting (XSS), Cross-Site Request Forgery (CSRF), Server-Side Request Forgery (SSRF), privilege escalation, or remote code execution.
LLM03: Training Data Poisoning
This occurs when LLM training data are tampered, introducing vulnerabilities or biases that compromise security, effectiveness, or ethical behaviour. Sources include Common Crawl, WebText, OpenWebText and books.
LLM04: Model Denial of Service
Attackers cause resource-heavy operations on LLMs, leading to service degradation or high costs. The vulnerability is magnified due to the resource-intensive nature of LLMs and the unpredictability of user inputs.
LLM05: Supply Chain Vulnerabilities
LLM application lifecycle can be compromised by vulnerable components or services, leading to security attacks. Using third-party datasets, pre-trained models, and plugins can add vulnerabilities.
LLM06: Sensitive Information Disclosure
LLMs may inadvertently reveal confidential data in its responses, leading to unauthorized data access, privacy violations, and security breaches. It’s crucial to implement data sanitization and strict user policies to mitigate this.
LLM07: Insecure Plugin Design
LLM plugins can have insecure inputs and insufficient access control. This lack of application control makes them easier to exploit and can result in consequences such as remote code execution.
LLM08: Excessive Agency
LLM-based systems may undertake actions leading to unintended consequences. The issue arises from excessive functionality, permissions, or autonomy granted to the LLM-based systems.
LLM09: Overreliance
Systems or people overly depending on LLMs without oversight may face misinformation, miscommunication, legal issues, and security vulnerabilities due to incorrect or inappropriate content generated by LLMs.
LLM10: Model Theft
This involves unauthorized access, copying, or exfiltration of proprietary LLM models. The impact includes economic losses, compromised competitive advantage, and potential access to sensitive information.
Turning off seccomp sandbox in vsftpd
21st September 2013
Within the last week, I set up a virtual web server using Arch Linux to satisfy my own curiosity, since the DIY nature of Arch means that you can build up exactly what you need without having any real constraints put upon you. Something that didn't surprise me about this was that it took me more work than the virtual server that I created using Ubuntu Server, yet I didn't expect Proftpd to be missing from the main repositories. Though the package can be found in the AUR, I didn't fancy the prospect of dragging more work on myself, so I went with vsftpd (Very Secure FTP Daemon) instead. In contrast to Proftpd, this is available in the standard repositories and there is a guide to its use in the Arch user documentation.
However, while vsftpd worked well just after installation, connections to the virtual FTP soon failed with FileZilla began issuing uninformative messages. In fact, it was the standard command line FTP client on my Ubuntu machine that was more revealing. It issued the following message that let me to the cause after my engaging the services of Google:
500 OOPS: priv_sock_get_cmd
With version 3.0 of vsftpd, a new feature was introduced, and it appears that this has caused problems for a few people. That feature is seccomp_sandbox and it can be turned off by adding the following line in /etc/vsftpd.conf:
seccomp_sandbox=NO
That solved my problem, and version 3.0.2 of vsftpd should address the issue with seccomp sandboxing anyway. In case, this solution isn't as robust as it should be because seccomp is not supported in the Linux kernel that you are using, turning off the new feature still needs to be an option, though.