Infostealer infections rarely trigger alarms. Early detection depends not on spotting the malware itself, but on recognizing subtle signs of its aftermath. They happen fast, leave few traces, and often occur on devices outside of your visibility. But they do leave behind signals — if you know what to look for.

Here are common signs that an infostealer may be active in or around your organization:

• Unexplained logins from unusual devices or patterns — such as new user agents, login times outside policy windows, or logins without MFA challenges (if visible through logs or identity providers)

• Persistent session anomalies — such as long-lived sessions across multiple geographies or reuse of expired tokens

• Abuse of internal trust — such as phishing emails from real employee accounts

• Privileged account activity outside normal behavior — including escalation, configuration changes, or access to high-risk systems

• Login attempts using credentials tied to inactive, legacy, or offboarded accounts — often the first assets tried by attackers

• New or unmanaged devices accessing internal systems — especially if they appear suddenly in SSO logs, access telemetry, or aren’t part of the corporate inventory

While none of these signs confirm an infostealer infection, they often appear in the wake of one. Early detection depends on connecting weak signals — across devices, identities, and session behavior — before they escalate into a breach