Cybersecurity professionals need to understand the distinction between indicators of compromise and indicators of attack in order to properly detect and respond to threats. While these terms are sometimes used interchangeably, they refer to different types of threat intelligence that serve distinct purposes.
In quick summary, indicators of compromise (IOCs) provide evidence that a system has been compromised by an attacker, while indicators of attack (IOAs) refer to signs that an attack campaign is underway or imminent. IOCs help organizations determine if they’ve been breached, while IOAs allow them to anticipate attacks before damage is done.
We’ll explore the key differences between these two types of cyber threat intelligence in more detail below.
What are Indicators of Compromise (IOCs)?
Indicators of compromise are forensic artifacts or patterns that signify a network intrusion or data breach has occurred. IOCs provide tangible evidence that a hacker was able to gain access to and likely steal data from a system.
Some examples of IOCs include:
- Malicious file hashes
- Malicious domains or IP addresses
- Anomalous DNS requests
- Suspicious registry keys or system file changes
IOCs are identified during or after an attack and they enable incident responders to determine the scope of a breach. By scanning for matching IOCs, analysts can check if other systems were impacted as part of the same campaign.
IOCs are an essential part of post-breach forensics and damage assessments. Their presence confirms that an attacker successfully infiltrated environments and achieved their objectives. Responders leverage IOCs to hunt for other affected assets that may be sitting undiscovered within networks.
How are IOCs generated?
IOCs originate directly from investigations of compromised hosts and from malware analysis. When an organization identifies that an attack occurred, analysts will dig into forensic artifacts on affected systems to extract details that signify the breach. These identifiable traces become IOCs that defenders can use to scan for related infections.
Security researchers also generate IOCs by reverse engineering malware samples. By picking apart malware code, analysts can extract tell-tale indicators associated with the specimen. These may include communication protocols, encryption algorithms, command and control addresses, and other attributes. Researchers share these technical malware indicators to help others detect related infections.
What are some key sources of IOCs?
Some of the top sources that cybersecurity teams utilize to gather IOCs include:
– Antivirus and EDR vendors: Security vendors extract and publish IOCs from analyzed samples, often within automated platforms.
– CERTs: Cyber emergency response teams in both the public and private sector share IOCs from incidents they analyze.
– ISACs: Information sharing and analysis centers distribute IOCs relevant to their sectors, such as financial services or electricity.
– Commercial threat intelligence platforms: Many threat intel services curate and validate IOC collections relevant to their clients.
– Open sources like VirusTotal: Researchers share malicious file hashes and other IOCs via public platforms.
– Internal forensic investigations: An organization’s own incident response efforts generate proprietary IOCs.
By leveraging these collective resources, security teams can maximize their visibility into relevant threats facing their organization based on IOCs.
What are Indicators of Attack (IOAs)?
Indicators of attack refer to early warning signs that an attack is imminent or underway. While IOCs signify historical evidence of compromise, IOAs provide actionable intelligence to anticipate and mitigate emerging attacks.
IOAs allow defenders to take proactive measures against an attack campaign in the planning stages, reconnaissance phase, or at the point of intrusion. With sufficient IOAs, organizations can thwart attacks before any real damage is done.
Examples of IOAs may include:
- Suspicious vulnerability scanning against networks
- Unusual spikes in DNS errors
- Common malware command and control patterns
- Known malicious domains being registered
- References to an organization on hacker forums
Spotting these types of early attack behaviors provides an opportunity to block threats before critical assets are compromised. IOAs also feed into threat hunting efforts that seek to root out adversaries that have already managed to slip past outer defenses.
Where do IOAs come from?
IOAs are generated via threat intelligence sources that provide visibility into the tactics, techniques and procedures (TTPs) of attackers. This may include:
– Monitoring hacker communications on forums and chat servers
– Analyzing malware campaigns at their earliest stages
– Tracking key stages of an attack kill chain
– Gathering details from intelligence agencies and law enforcement around actor activity
To translate this information into action, intelligence analysts identify key patterns that align with preparatory steps in an attack. For example, a spike in vulnerability scans against a target could signal an impending campaign. These TTP-based insights then become tactical IOAs.
The IOAs are disseminated to cybersecurity teams, giving them an early look at what types of suspicious activities they should hunt for within their environments.
Comparing IOCs vs. IOAs
While IOCs and IOAs both provide valuable threat intelligence, they differ in some key ways:
Strategic purpose
- IOCs are reactive – They show that an attack was successful and help ascertain the impact.
- IOAs are proactive – They surface early attack stages and support blocking threats.
Details contained
- IOCs contain forensic evidence from within compromised entities.
- IOAs describe external behaviors and reconnaissance by attackers.
Generation methods
- IOCs originate from analyzing IT artifacts on affected systems.
- IOAs derive from researching hacker TTPs and anticipating their next moves.
Timing
- IOCs emerge after a successful breach.
- IOAs appear in early attack stages, often weeks or months before.
Scope
- IOCs focus on details of a specific incursion.
- IOAs relate to broad attack campaigns impacting many targets.
Deployment
- IOCs feed scanning tools to uncover compromised devices.
- IOAs support proactive threat hunting to find attackers.
So in summary:
- IOCs help understand scope and impact of breaches.
- IOAs allow blocking of emerging attack campaigns.
Cybersecurity teams need both forms of data to defend their environments against advanced persistent threats.
Using IOCs and IOAs Together for Defense
IOCs and IOAs provide complementary value for identifying threats and securing the enterprise. Here are a few examples of how they can be used together:
Augment threat hunting
Threat hunters leverage IOAs to surface signs of potential attackers moving through the environment. When suspicious activity is detected, IOCs can help determine if a breach occurred.
Prioritize incidents
An IOA may indicate your organization is being targeted by an advanced attacker. Related IOCs can reveal if mission critical assets were compromised, raising the severity.
Enrich alerts
IOAs provide context about cyber campaigns targeting the organization. IOCs give alarms more meaning by linking them to known attacks.
Fix security gaps
IOAs may reveal attackers performing reconnaissance scans for specific vulnerabilities. The organization can then check IOCs for related exploits and patch affected systems.
Anticipate future moves
Analysts can leverage historic IOCs to predict the TTPs and IOAs that attackers may rely on in upcoming campaigns. Defenders get an edge in preparing to combat the next moves.
Guide access controls
IOCs tied to compromised accounts can be used to limit access and privileges to sensitive data. IOAs help determine when tightened controls may be warranted.
By leveraging IOCs and IOAs as a unified information set, organizations multiply the value of their threat intelligence. This empowers security teams to achieve visibility across both historical and emerging attack activities.
Conclusion
Indicators of compromise and indicators of attack provide complementary lenses into cyber threats facing modern organizations. While IOCs illuminate successful breaches after the fact, IOAs help analysts look around corners to anticipate the moves of advanced attackers and proactively defend their networks.
Security teams must leverage both real-time IOAs and forensic IOCs to understand attackers’ capabilities, objectives and tactics. This enables fast and accurate detections combined with robust incident response. Organizations must build comprehensive strategies relying on both forms of threat intelligence to achieve resilience against targeted and persistent attacks moving forward.