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Indicator of Compromise

Definition: An Indicator of Compromise is forensic evidence that is identified on a computer or network system suggesting a security breach has occurred or an intrusion is underway. Common types of Indicator of Compromise include IP addresses, URLs, and file hashes that are associated with malicious activity.

In cyber security, Indicators of Compromise are essential for the early detection of potential threats, as they help organisations identify ongoing or past intrusions quickly. The prompt identification of Indicators of Compromise allows for timely incident response and mitigation strategies to be put into action, thereby reducing potential damage to systems or loss of data.

Indicators of Compromise serve a substantial role in security operations, as they are used by threat hunting teams and security monitoring systems to uncover suspicious activities. Cyber security professionals analyse these indicators against logs, network traffic, and endpoint systems to detect anomalies that signify malicious intent.

One of the major challenges is distinguishing between normal system activities and IoCs that signify an actual threat. Therefore, continuous refinement and correlation of these indicators against broader threat intelligence are required. This includes leveraging Security Information and Event Management (SIEM) systems to aggregate and analyse log data across an organisation’s IT infrastructure, aiding in the faster recognition and investigation of Indicators of Compromise.

Key Characteristics:

  • Forensic evidence of network or system intrusion
  • Includes IPs, URLs, file signatures, and even unconventional patterns of behaviour
  • Facilitates early detection and response to cyber threats
  • Requires ongoing analysis and correlation with threat intelligence


  • Real-World Example: In the aftermath of a suspicious network outage, IT security analysts identify an Indicator of Compromise in the form of an unknown executable file attempting to communicate with a known malicious external IP address, signalling a malware infection on the network.
  • Hypothetical Scenario: A cyber security team notices an Indicator of Compromise when they observe abnormal access patterns in the database logs that are uncharacteristic of normal user behaviour, hinting at the possibility of a compromised insider account.

Related Terms:

  • Malware Infection: Often indicated by IoCs, malware infections can lead to a range of cybersecurity issues, from data leakage to system takeover.
  • Threat Hunting: Proactive cybersecurity activities focused on searching for IoCs within an IT infrastructure to pre-emptively disrupt cyber threats.
  • SIEM (Security Information and Event Management): A security solution that aggregates data and identifies anomalies or trends that might serve as IoCs.
  • Tactics, Techniques, and Procedures (TTPs): Descriptions of the behavior of cyber attackers, which can sometimes be deduced or illuminated by analysing IoCs.

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