Signs of ransomware

A ransomware attack is one of the most serious threats facing UK businesses today. It only takes a single employee opening a malicious file or an attacker exploiting a weakness in your operating systems for ransomware activity to begin. Within minutes, files are encrypted, devices are locked, and operations can grind to a halt.

If you are reading this because you are currently experiencing a ransomware incident, stop now and contact Zensec immediately. This is not a situation to manage alone. Our 24/7 team can contain the threat, support system recovery, and help you protect your reputation.

For those looking to prepare or understand the threat more deeply, this blog explains the key signs of ransomware and what to do if you spot them. Our mission is to bring calm and clarity when your organisation needs it most.

Here are the five key signs of ransomware every UK organisation should recognise.

Unusual file activity

One of the clearest indicators of a ransomware infection is strange behaviour in your files. You may notice:

• File names changing suddenly or being replaced with unusual extensions like .exe or unfamiliar code.
• The encryption process starting silently in the background, locking a significant amount of data within a short period.
• Inability to open all the files you normally use, with messages saying they are encrypted or corrupted.

If this occurs, treat it as an urgent signal of compromise. Attackers may already have gained a foothold in your network, and time is critical to stop further spread.

Ransom notes appearing on screen

Most ransomware variants eventually reveal themselves with a clear ransom note. This can show up as a text file, a pop-up message, or even a full-screen lock. It will typically demand payment in cryptocurrency and threaten permanent data loss if instructions are not followed.

A ransom note is not just a demand for money. It is proof that cybercriminals have already gained control over your systems. In some cases, attackers may also warn that they will publish stolen data online, adding the risk of data exfiltration and potential regulatory consequences.

Slow or unresponsive systems

A sudden slowdown in your computers, servers, or cloud servers can indicate active ransomware activity. This may be caused by the encryption process, as large volumes of files are being locked.

Watch out for:

• High CPU or memory usage with no obvious explanation
• Multiple infected devices showing the same slowdown at the same time
• Users reporting they no longer have access to shared folders or that services are unavailable

These are strong signs that attackers are attempting to gain access to your wider infrastructure, targeting critical systems that support daily operations.

Suspicious network traffic

Another key indicator is abnormal behaviour in your network traffic. Monitor network traffic closely for:

• Unexplained spikes in outbound connections
• Data flowing to unfamiliar IP addresses or regions
• Ransomware activity communicating with command-and-control servers

A properly configured intrusion prevention system or advanced security software can help detect this behaviour early. Catching it at this stage may allow you to stop the attack before it causes a significant amount of damage.

Locked devices or accounts

If users report being locked out of computers, applications, or entire systems, it is often the final and most visible stage of a ransomware attack. At this point:

• Victims lose longer access to files, emails, and business-critical tools
• The organisation may see widespread downtime of services
• The attacker has succeeded in denying access until a payment is made

At this stage, the priority is to contain the threat, protect backups, and begin system recovery with professional support.

How to respond to signs of ransomware

If you detect any of these warning signs:

1. Immediately disconnect affected devices from your network to stop further spread
2. Engage your security team and activate your incident response plan
3. Contact Zensec’s cyber incident response specialists to assess, contain and support system recovery

Never attempt to manage a ransomware situation alone. A misstep can lead to further compromise, permanent data loss, or the exposure of sensitive data.

Preventing ransomware attacks

While recognising the signs of ransomware is crucial, prevention is always better than cure. Best practices include:

• Keeping security software and antivirus tools updated
• Applying patches to fix known vulnerabilities in operating systems
• Taking regular backups and following the 3-2-1 rule (three copies, two storage types, one offsite)
• Using multi-layered detection and monitoring to spot abnormal ransomware activity
• Training every user to recognise suspicious emails and avoid downloading infected attachments

These steps not only protect against ransomware but also strengthen resilience against other types of malware and cyber threats.

What happens if you get ransomware

If ransomware strikes, the impact can be severe. Businesses may face:

• Downtime and disruption of critical services
• Permanent data loss if backups are unavailable
• Costs linked to recovery, regulatory reporting, and reputational harm
• Pressure from attackers to meet a ransom demand or risk having data leaked

With expert support, many organisations can recover without paying criminals. Zensec focuses on helping clients restore operations, regain access to data, and rebuild a clean network environment.

Final thoughts

Being able to spot the signs of ransomware early can make the difference between a minor disruption and a business-crippling event. By combining vigilance, strong security software, and expert cyber incident response, UK businesses can stay prepared for this evolving threat.

If you suspect ransomware activity in your environment, contact Zensec immediately. Our team works 24/7 to bring calm, clarity and control when you need it most.