Indicators of compromise

What is IOC in cybersecurity?

Indicators of compromise (IOC) in cybersecurity refers to clues or evidence that suggest a network or system has been breached or attacked. For example, IOCs can be unusual network traffic behavior, unexpected software installations, user sign-ins from abnormal locations, and large numbers of requests for the same file.

What's the difference between indicators of compromise and indicators of attack?

Infosec teams use both indicators of compromise and indicators of attack (IOA) to analyze a security event. IOAs signal an attack occurring in real time, whereas IOCs are evaluated after an attack to better understand the incident.

What types of data are considered IOCs?

IOCs encompass diverse types of data, including:

• IP addresses
• Domain names
• URLs
• Email addresses
• Network traffic patterns
• Filenames, paths, and hash files

What are the challenges in managing IOCs effectively?

Monitoring and analyzing IOCs presents a number of challenges. The sheer volume alone of IOCs detected daily can overwhelm security teams, in addition to keeping IOCs up to date in today's rapidly evolving threat landscape. However, even the most effective IOC management is not enough to reduce risk of threats and prevent attacks.

Managing IOCs is a reactive approach that relies on historical data of known threats. New, advanced threats may evade indicator-based threat detection. IOCs are more effective when combined with proactive measures to detect threats faster, such as endpoint security, real-time threat intelligence, threat management platforms, and identity access controls.

How do IOCs help detect cyberthreats?

IOCs in cybersecurity are evidence that an attack may have occurred. Security teams or technologies monitor network traffic, user and device behaviors, file attributes, and other data for irregularities or suspicious patterns. Log data that matches known indicators of compromise alert teams to investigate and mitigate these potential threats.

While IOCs are useful for spotting known threats, they are reactive by nature and may not identify unknown or advanced attacks. To proactively identify today's sophisticated threats, organizations often use threat intelligence platforms to track IOCs in their environment and get real-time information on the latest threats and mitigations.

How does monitoring for IOCs help incident response?

Security teams monitor threat intelligence feeds, security logs, and network traffic for IOCs that require investigation and remediation. Regular IOC security monitoring enables:

Early detection: Early identification of IOCs alert teams to breaches or attacks and empower them to rapidly eliminate the threat and restore operations.

Prioritization: Monitoring IOCs helps prioritize incidents for remediation based on their severity to address the most critical threats promptly.

Response improvement: Tracking and documenting IOCs helps response teams learn from each event and develop a more effective incident response plan (IRP).

Lower security risk: After recovering from an attack, forensic analysis of the event and its indicators helps uncover vulnerabilities in systems and processes. This analysis helps the team develop more effective defenses against similar attacks in the future.

How are IOCs categorized in cybersecurity investigations?

Network-based IOCs

Network IOCs signal suspicious activity on a network, like domains, IP addresses, and URLs known to be malicious. Unusual traffic behavior, such as an increase in web traffic to a specific website, can also indicate network compromise. Network monitoring tools work to detect these types of IOCs, like security information and event management (SIEM) solutions and intrusion detection systems (IDS).

File-based IOCs

File-based indicators of compromise suggest that malicious downloads or malware has infected system files. Sandboxing tools or endpoint detection and response (EDR) software are commonly used to scan files for known malicious file hashes, paths, or filenames.

Behavioral IOCs

Behavioral IOCs draw from deviations in normal activities and patterns. Privilege escalation, numerous requests for the same file, or repeated login attempt failures are examples of behaviors that indicate a system attack may have occurred. User and entity behavior analytics (UEBA) solutions monitor user and device communication patterns for suspicious behavior that differs from an established baseline.

Host-based IOCs

Host-based IOCs uncover potentially malicious activity on individual computers, systems, or other endpoints. These include unexpected changes to system settings, changes in system permissions, or suspicious processes running on a device. To monitor endpoints for threats and manage host-based IOCs, EDR or extended detection and response (XDR) tools can be employed.

What are common examples of IOCs?

Unusual sign-in activity

Irregular details of a user or device logging in to an account can indicate an attempted or successful breach. Multiple failed login attempts, login from an abnormal location, or access to files unusual for a user may suggest an attacker has hacked an account.

Network traffic anomalies

When network traffic patterns deviate from the norm, certain anomalies may suggest a cyberattack has taken place. For example, a sudden spike in data transfers or communication with a known malicious IP address can indicate an attacker attempted to steal data.

Privileged account irregularities

Unexpected use of privileged accounts can signal an insider threat or a compromised account. Administrators changing user-access settings or accessing nonstandard resources can indicate an attempt to gain unauthorized access.

Substantial number of file requests

A sudden surge in requests for sensitive files, particularly from a single user or IP address, can signify an attacker's efforts to access restricted information.

DNS request anomalies

Irregularities in Domain Name System (DNS) queries, such as requests for known malicious domains, can point to an attacker's attempts to establish command and control communication with the organization's server.

Configuration changes

Unexpected or unauthorized changes to system configurations, firewall rules, or access security policies may indicate an attacker's presence and attempts to weaken defenses.

Suspicious processes running

Unknown processes running in a system's task manager, particularly those with usual attributes or names, may suggest a malware infection.

IOC solutions and tools

Monitoring IOCs is crucial for identifying attacks and resolving them quickly. Understanding these indicators of compromise also provides deep insight that enables teams to better mitigate vulnerabilities, improve defense mechanisms, and resolve security incidents faster.

While IOCs are a critical tool in cybersecurity, they are not standalone solutions. IOC monitoring is most effective when paired with advanced security solutions that safeguard your organization against evolving threats, such as:

Next-generation intrusion prevention system (NGIPS)

An NGIPS utilizes IOCs to detect threats. Advanced NGIPS systems continuously monitor user and device behavioral IOCs, deliver real-time contextual threat analysis, enforce security across public and private clouds, and support network segmentation for robust threat protection.

Endpoint security platforms

Endpoint security solutions are designed to protect devices, or endpoints, connected to a network. Extended detection and response (XDR) solutions monitor endpoint, email, server, cloud, and network activity for behavioral indicators of compromise. This level of visibility paired with AI and machine learning enables automated and guided threat remediation prioritized by greatest risk.

Security information and event management (SIEM)

SIEM solutions aggregate log and event data, threat intelligence, and security alerts from systems across an IT environment. When activities correlate with known IOCs, a SIEM solution generates prioritized alerts based on predefined policies and enables automated responses to the potential security incident.

Identity access management (IAM)

IAM solutions manage user access to resources based on their digital identities and level of access. To prevent unauthorized access to sensitive resources, these solutions use multiple factors to authenticate user identity, and continuously monitor user and device behavior for IOCs.

Network segmentation

Network segmentation enforces granular access control by dividing the network into smaller parts. In the event of IOCs detecting a breach, segmentation can prevent attacks from spreading laterally within the network, minimizing its damage.

Threat intelligence platforms

Threat intelligence platforms are cybersecurity tools that aggregate and analyze vast amounts of global data from various sources, including IOCs, to provide actionable insights about emerging cybersecurity threats. Integrating cyberthreat intelligence with your security architecture enhances threat detection and response solutions, allowing organizations to proactively defend against evolving cyberthreats based on real-time intelligence.