Ransomware has become one of the most frequent and dangerous threats in the world of cybersecurity, and at TecnetOne, we’re seeing it increasingly affect businesses of all sizes. Although many only associate it with the dreaded ransom screen, the truth is that several warning signs often appear before reaching that point, allowing the attack to be detected in time and the damage minimized.
These ransomware indicators are clear clues that something’s not right: strange system behavior, unexplained file changes, or unusual access that could mean an attack is already underway or about to happen. Identifying them quickly can save you from data loss, financial damage, and major headaches.
That’s why we created this guide to show you the seven most important signs to watch for—and how to act if you start noticing any of them.
A ransomware attack happens when a type of malware encrypts the files on your computer and prevents you from accessing them until you pay a ransom to receive the decryption key. In simple terms: it hijacks your information and demands money in exchange.
Once ransomware installs itself, a screen or pop-up usually appears informing you that your files have been encrypted and that you need to pay if you want to recover them. This type of malware also tends to change file names and extensions, making them unrecognizable (which is why monitoring suspicious extensions is key to detecting malicious activity early).
The impact is swift and can be devastating, especially for businesses that rely on constant access to their data. An attack can cause operational downtime, financial losses, drops in productivity, and even total data loss if proper backups aren’t in place.
That’s why early detection is so important. Spotting strange behaviors or unusual activity in your system allows you to respond before the damage becomes irreversible. Security tools and the operating system itself play a key role by monitoring file execution and detecting anomalies that could signal the presence of ransomware.
Before a ransomware attack fully unfolds, it almost always leaves behind small clues. These are warning signs that, if identified in time, can stop the attack from progressing and encrypting all your data.
These signs can range from a suspicious email to strange network activity or unauthorized access. While they might seem like minor issues at first, they are actually key indicators that something is wrong.
Catching these symptoms early allows you to take preventive action, strengthen your security, and stop the attack before it's too late.
Below are the most common signs you should watch for—and how each one can help you identify ransomware activity in time.
Ransomware attacks often begin with a simple email. Cybercriminals send messages that look legitimate but are designed to trick you into opening a malicious file or sharing sensitive information. A single click on an infected attachment is enough to set the attack in motion.
The best defense is education: training your team to recognize fake emails, shady senders, and suspicious links greatly reduces risk. Implementing measures like SPF, DKIM, and DMARC also helps validate legitimate emails and block phishing attempts before they hit the inbox.
If you start seeing files with unknown extensions or unrecognized names, it’s a clear sign something’s wrong. Ransomware typically renames and encrypts files to make them inaccessible—this is one of the clearest signs that an attack has already started.
Catching these changes early lets you react before more data is encrypted. This is a warning sign you should never ignore.
Another major red flag is unusual behavior on your network. If you notice scans no one on your team performed or unexpected device connections, it could mean an attacker is mapping your infrastructure to find vulnerabilities.
Network scanners are often used to prepare the ground before launching encryption, so any out-of-the-ordinary activity warrants immediate investigation. Continuous monitoring is key to staying ahead of these moves.
Active Directory is a prime target in ransomware attacks because it allows control over users and devices within a network. Attackers exploit vulnerabilities or use remote access like RDP to break in, then deploy tools like BloodHound or ADFind to gather information and escalate privileges.
If you detect suspicious access attempts, strange queries, or the use of such tools, it could indicate someone is trying to take over your domain. Early detection helps protect critical systems.
When attackers want to steal credentials, they often turn to advanced tools like MimiKatz, which can extract passwords, hashes, and even Kerberos tickets directly from memory. Finding these tools running in your systems is a red alert.
That’s why it’s essential to monitor processes, review logs, and have EDR solutions that can flag suspicious activity. Regular audits also help catch intrusions before they progress.
If your antivirus or security solutions stop working without explanation, it may mean an attacker has already gained admin access. Many ransomware groups try to uninstall or disable defenses before launching encryption.
Finding software removal tools on your network is a serious warning that demands immediate action. The faster you respond, the less impact the attack will have.
An unusually slow network can also be a clue. When ransomware starts encrypting files, traffic spikes—more modifications, more uploads, more data movement.
Analyzing traffic helps spot these anomalies, though false positives are possible. Still, combined with other signs, this can strongly suggest malicious activity.
These signs, even if they seem small, can mean the difference between stopping an attack in time or facing massive data loss. Detecting them early is key to protecting your business and keeping your systems secure.
Read more: Ransomware 2025: Threats, Costs, and How to Defend Your Business
Detecting a ransomware attack before it causes serious damage is key to protecting your business. To do this, several detection techniques are available, each working from different angles: signature-based analysis, network traffic monitoring, and behavioral observation of files and processes. Each method has its pros and cons, and understanding them will help you choose the most effective strategy for your organization.
Real-time detection—which monitors unusual file changes and system behavior—is especially useful because it identifies attack signals instantly and allows for quick action to minimize the impact.
This method works by comparing suspicious files to a database of known malware. If it matches a registered “signature,” the file is automatically blocked. Its main strength is accurately identifying known ransomware variants.
The issue: attackers constantly evolve. If a new or modified variant appears, this method might not detect it. That’s why, while useful, it shouldn’t be your only line of defense.
Network traffic analysis helps detect strange patterns, suspicious connections, or unusual data movement that could indicate an attack is underway.
Tools like IPS (Intrusion Prevention Systems) monitor the network in real time and can detect communication between ransomware and its command-and-control servers.
This technique is powerful but can also generate many false positives, sometimes causing “alert fatigue.” Still, when combined with other methods, it provides a comprehensive view of what’s happening in your environment.
Unlike signature-based detection, this approach doesn’t rely on recognizing specific malware. It focuses on spotting unusual behavior: rapidly changing files, processes making massive modifications, or activities that don’t make sense in the normal system flow.
The best part of this method is its ability to detect even new or unknown ransomware and its tendency to produce fewer false positives. Its downside is that in some cases, it may take a little longer to respond, as it needs to observe patterns before triggering an alert.
Early detection is essential, but prevention is just as important. To reduce the risk of falling victim to an attack, you need a comprehensive approach that combines technology, processes, and training.
Here are some essential practices:
Train your team to recognize phishing emails—one of the main entry points.
Keep all security software up to date, from antivirus tools to advanced protection solutions.
Perform frequent backups and store them in secure or offline locations to ensure recovery after an attack.
Protect your endpoints, which are often the first targets of ransomware.
Segment your network, so if one device is infected, the malware can’t spread easily.
Use application whitelisting to block unauthorized software from running.
Implementing these measures not only strengthens your security posture but also makes attackers’ jobs significantly harder.
When a ransomware attack happens, every minute counts. Acting fast is critical to prevent the issue from spreading and causing irreversible damage. The first step is always to isolate affected devices by disconnecting them from the network to stop the malware’s spread.
Next comes the eradication phase, which usually involves wiping the compromised devices and restoring data from clean, verified backups.
Recovery doesn’t end there. It’s essential to validate that the restored system functions correctly, update software and apply pending patches, perform thorough scans with up-to-date security tools, and document the incident to strengthen your cybersecurity strategy. Every incident is a learning opportunity to reinforce your defenses.
This is where TecnetOne can make a difference. Our specialized Incident Response service is designed to act swiftly and precisely in the face of ransomware attacks.
Our team provides immediate containment of the incident, forensic analysis to identify the source, ransomware removal, data recovery from secure backups, and infrastructure hardening to prevent future attacks.
We also offer post-incident recommendations and support so your company comes out more protected than before. With a fast, professional response like TecnetOne’s, you can turn a critical attack into a chance to improve your cybersecurity posture and ensure your business continuity.