The most dangerous assumption in cybersecurity is that you would know if you had been breached. The uncomfortable truth: most organizations discover they have been compromised months after the fact — and usually not by their own detection systems.

Here are five signals that often go unnoticed but suggest an intruder may already be operating inside your network.

Sign 01

Logins From Unexpected Locations

If an employee account logs in from Germany at 3am local time while the employee is asleep in Tel Aviv, that is a red flag. Many organizations never review login geography at all. Geo-fingerprinting catches credential theft that would otherwise go completely undetected.

Sign 02

Unusual After-Hours Network Activity

Attackers typically operate during off-hours when monitoring is reduced. Spikes in network traffic at 2am, file access patterns outside business hours, or admin tool usage on weekends should never be dismissed as routine.

Sign 03

Accounts Accessing Resources They Normally Do Not

An attacker who gains access to a low-privilege account will immediately try to escalate — accessing admin panels, sensitive directories, or systems outside their normal scope. If a marketing account suddenly queries HR databases, that is privilege escalation behavior.

Sign 04

Unexplained Slowdowns or Crashes

Ransomware and data exfiltration both consume significant resources. If servers become unexpectedly slow, if processes spike without explanation, or if systems crash without a clear cause, these can be early signs of malicious activity running in the background.

Sign 05

Unknown Devices on the Network

Attackers sometimes add compromised devices to the network to maintain persistent access. If your device inventory does not match what is actually connected, you have an unresolved anomaly that demands investigation.

🚨 If you have noticed any of these signs, act quickly. Evidence is time-sensitive. The longer an attacker remains undetected, the deeper their access and the more damage they can cause.

What to Do Right Now

The most reliable way to catch an intruder already inside your network is to deploy proprietary traps — decoy assets that only an attacker would touch. Purim NetGo can have traps active on your network within minutes. If someone is already inside, they will find one.