What Are Stealer Logs and Keyloggers? The Silent Threat Draining UK Businesses

There's a good chance that right now, somewhere on the dark web, your company's credentials are for sale. Not because you've been "hacked" in the traditional sense - but because one of your employees clicked the wrong link, downloaded the wrong file, or installed what looked like legitimate software.

Welcome to the world of stealer malware and keyloggers. And if you're not worried yet, you should be.

What Exactly Are We Talking About?

Keyloggers: Recording Every Keystroke

A keylogger is exactly what it sounds like - malicious software that records every single key pressed on an infected device. Every password typed. Every email composed. Every private message sent. Every credit card number entered.

The infected user has no idea it's happening. There's no popup, no slowdown, no warning. The malware silently captures everything and sends it back to criminals.

Stealer Malware: The Industrial-Scale Credential Harvester

Stealer malware takes things further. Rather than just logging keystrokes, these sophisticated programs actively raid infected devices for valuable data:

• Saved passwords from browsers (Chrome, Firefox, Edge - they're all vulnerable)
• Session cookies that let attackers bypass two-factor authentication entirely
• Cryptocurrency wallets and banking details
• Autofill data including addresses, phone numbers, and payment cards
• Browser history revealing which systems your business uses

This harvested data gets packaged into what's called a "stealer log" - a neat bundle containing everything a criminal needs to impersonate your employee and access your systems.

How Do People Get Infected?

The infection routes are depressingly mundane:

• Pirated software: That "free" version of Photoshop or Microsoft Office
• Cracked games: Downloaded from unofficial sources
• Fake browser extensions: Promising useful features
• Phishing emails: With malicious attachments or links
• Compromised websites: Drive-by downloads that require no user action
• Malicious ads: Even on legitimate websites

The uncomfortable truth? Many infections happen on personal devices - laptops used for both work and personal browsing, or phones connected to company email. Your corporate security policies mean nothing when credentials are stolen from an employee's home computer.

The Three Ways This Destroys UK Businesses

1. Your Staff Are Already Compromised

When an employee's device is infected, attackers gain access to:

Corporate email accounts - Reading sensitive communications, sending emails as your staff, intercepting password reset links.

Cloud services - SharePoint, Google Drive, Dropbox - wherever your business stores files.

Internal systems - CRM platforms, accounting software, HR systems containing personal data.

VPN credentials - The keys to your entire corporate network.

A single infected employee can expose your entire organisation. And here's the terrifying part: the average time between infection and detection is many months. That's a long time for criminals to have full access to your systems.

2. Your Customers Are at Risk

When customer-facing credentials are stolen, the damage multiplies:

Account takeover attacks - Criminals log into your customers' accounts, change delivery addresses, make fraudulent purchases, or steal stored payment methods.

Data theft - Customer databases accessed and exfiltrated for sale on dark web marketplaces.

Reputational destruction - Once customers learn their data was compromised through your systems, trust evaporates overnight.

Regulatory fines - The ICO doesn't care that the infection happened on a personal device. If customer data was exposed, you're liable. GDPR fines can reach 4% of global annual turnover.

3. Your Supply Chain Becomes a Weapon

This is where things get truly nasty. Your suppliers and partners face the same threats -and their compromised credentials become your problem.

Vendor email compromise - Attackers intercept legitimate invoices and change payment details. UK businesses lose millions annually to this scam.

Software supply chain attacks - Compromised supplier systems push malicious updates to your infrastructure.

Trusted access abuse - Partners with VPN access or system integrations become backdoors into your network.

Cascading breaches - One compromised supplier can expose dozens of businesses they work with.

The Dark Web Marketplace

Stolen credentials aren't just used by the attackers who harvest them. They're commodities, traded on underground marketplaces with remarkable efficiency.

Pricing varies based on value:

• Basic credentials sell for relatively little
• Corporate accounts with business system access command higher prices
• Banking and financial logins are more valuable still
• Admin credentials with VPN or privileged access fetch the highest prices

Logs are sold in bulk. Buyers filter by country, company domain, or service. Someone right now could be searching for credentials ending in your company's email domain.

The criminals who buy these logs aren't sophisticated hackers - they're opportunists following tutorials, using point-and-click tools to exploit purchased access. The barrier to entry has never been lower.

The Wake-Up Call UK Businesses Need

The National Cyber Security Centre (NCSC) consistently warns that credential theft is one of the most common attack vectors against UK businesses. Yet most organisations have no visibility into whether their credentials are already circulating on dark web marketplaces.

Consider these questions:

• Do you know if any employee credentials are currently for sale?
• Would you detect a login from stolen session cookies?
• Are you monitoring for your company domains in stealer log databases?
• Could you identify an infected employee device today?

If you answered "no" to any of these, you're operating blind in an increasingly hostile environment.

What You Can Do Right Now

Immediate actions:

1. Deploy dark web monitoring - Know when credentials appear in stealer log databases
2. Enforce password managers - Eliminate browser-saved passwords that stealers target
3. Implement hardware security keys - Phishing-resistant MFA that session cookies can't bypass
4. Segment network access - Limit blast radius when credentials are compromised

Longer term:

1. Zero trust architecture - Verify every access request, every time
2. Endpoint detection and response - Identify infected devices before damage spreads
3. Regular security awareness training - Focus on the mundane infection routes
4. Supply chain security assessments - Your partners' security is your security

The Bottom Line

Stealer logs and keyloggers represent a fundamental shift in how businesses get compromised. There's no dramatic breach, no ransom note, no obvious attack. Just quiet credential theft, followed by patient exploitation.

The criminals are organised, efficient, and profitable. They're harvesting credentials at industrial scale, and UK businesses are prime targets.

The question isn't whether your organisation's credentials will end up on the dark web. It's whether you'll know about it before the damage is done.