Cybersecurity Glossary

Indicator of Compromise

Evidence suggesting that a system has already been breached.

What Indicator of Compromise means

Indicators include unfamiliar sign ins, new mailbox forwarding rules, unexpected administrative accounts, connections to known malicious addresses, and files appearing in unusual places. They are the signs to search for once you suspect something, and to alert on in advance where you can.

Why Indicator of Compromise matters for small businesses and nonprofits

Intrusions are typically discovered weeks after they begin, often by an outside party. Knowing the handful of indicators worth checking lets a small organisation confirm or dismiss a suspicion in an hour rather than a week.

What to do about Indicator of Compromise

Three steps to deal with Indicator of Compromise

  • Check for mailbox forwarding rules regularly, a classic and quiet sign of takeover
  • Alert on new administrative accounts and on sign ins from unexpected countries
  • Keep logs long enough to search backwards when an indicator appears

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