What are Indicators of Compromise (IoCs)? | An Easy Guide


An Indicator of Compromise (IoC) is a piece of information that indicates a potential security breach or cyberattack. Cybersecurity professionals use it to identify and respond to threats effectively. An IoC can be a file, IP address, domain name, registry key, or any other evidence of malicious activity. Cybersecurity professionals use IoCs to track down attackers, understand their methods, and prevent future attacks.

In today’s digital age, the growing threat of cybercrime has put organizations of all sizes and sectors on high alert. One of the most significant challenges enterprises face is detecting and responding to security incidents, including data breaches and system compromises before they can cause considerable damage. This is where IoCs come into play.

IoCs are critical instruments that help organizations identify and mitigate potential threats by providing early warning signs of malicious activities. This comprehensive guide will provide an in-depth overview of IoCs, including their definition, types, uses, and how to leverage them to enhance your organization’s security posture.


Before we dive deeper into IOCs, it’s essential to understand the difference between IOCs and IOAs (Indicators of Attack). IOCs are used to identify when an attacker has already compromised a system. On the other hand, IOAs are used to detect when an attacker is attempting to gain access to a system.

IOCs are typically used to detect and respond to specific security threats, while IOAs are used to detect and respond to a wide range of security threats. IOCs are generally more straightforward than IOAs and provide more detailed information about a potential security threat.

Types of Indicators of Compromise (IoCs)

Different types of Indicators of Compromise (IoCs) are used in cybersecurity. Some of these include:

  • File-based Indicators – These are associated with a specific file, such as a hash or file name.
  • Network-Based Indicators – Indicators associated with a network, such as an IP address or domain name.
  • Behavioral Indicators – These are indicators that are associated with the behavior of a system or network, such as unusual network traffic or unusual system activity. There are many Behavioral Indicators that MITRE Engenuity ATT&CK maps.
  • Artifact-Based Indicators – These are indicators associated with the artifacts left behind by an attacker, such as a registry key or a configuration file.

How do Indicators of Compromise (IoCs) Work?

IoCs are created through various means, such as threat intelligence, monitoring security logs, and analyzing network traffic. Once an IoC is identified, cybersecurity professionals or a SOC can use it to develop security measures that detect and prevent similar attacks. For example, if an IoC is a malicious IP address, cybersecurity professionals can block the IP address, preventing any communication between the attacker’s system and the organization’s network.

Why Are Indicators of Compromise (IoCs) Important?

Indicators of Compromise (IoCs) are essential because they help security teams detect and prevent cyber threats. IoCs can identify and mitigate cyber attacks, such as malware infections, phishing attacks, and other cyber threats. As a result, organizations can protect their systems and data from cybercriminals by detecting and mitigating these threats.

IoCs play a crucial role in identifying and mitigating potential threats to an organization’s security. By leveraging IoCs, organizations can:

  • Detect security incidents quickly – IoCs can help organizations identify security incidents and take action to prevent or mitigate potential damage.
  • Monitor for future threats – By monitoring for known IoCs, organizations can detect potential threats and take proactive measures to prevent them.
  • Improve incident response – IoCs can help organizations develop more effective incident response plans by providing early warning signs of malicious activities.
  • Share threat intelligence – IoCs can be shared between organizations, enabling them to collaborate and pool resources to identify and mitigate potential threats more effectively.

Types of Indicators of Compromise

There are several types of IoCs, each with unique characteristics and uses. These include:

1. Network IoCs

Network IoCs are indicators that suggest suspicious activity on a network. These can include unusual traffic patterns, connections to known malicious IP addresses or domains, and unexpected protocols or ports being used. Network IoCs can be detected through various network monitoring tools, including Intrusion Detection Systems (IDS) and Security Information and Event Management (SIEM) systems.

2. Host-Based IoCs

Host-based IoCs are indicators that suggest suspicious activity on a specific computer or system. These can include unusual file activity, suspicious processes or services running, and unexpected changes to system configuration settings. Host-based IoCs can be detected through various endpoint security solutions, including Endpoint Detection and Response (EDR) or XDR (Extended Detection and Response) tools.

3. File-Based IoCs

File-based IoCs are indicators that suggest the presence of malicious files or malware on a system. These can include things like file hashes, filenames, and file paths. File-based IoCs can be detected through various file-scanning tools, including EDR software and Sandboxing tools.

4. Behavioral IoCs

Behavioral IoCs are indicators that suggest suspicious user activity on a network or system. These can include multiple failed login attempts, unusual login times, and unauthorized access to sensitive data. Behavioral IoCs can be detected through user monitoring tools, including User and Entity Behavior Analytics (UEBA) solutions. SentinelOne XDR uses a combination of behavioral IoCs, advanced analytics, machine learning, and behavioral analysis to detect and respond to threats in real time.

Examples of Indicators of Compromise

1. Unusual Outbound Network Traffic

Anomalies in network traffic patterns and volumes are the most common signs of a security breach. Keeping intruders out of your network is becoming increasingly difficult. Monitoring outgoing traffic for potential Indicators of Compromise can be helpful. When an intruder attempts to extract data from your network or an infected system relays information to a command-and-control server, unusual outbound network traffic may be detected.

2. Geographic Abnormalities

Another common type of indicator of compromise is geographic abnormalities. If an unusual amount of traffic comes from a particular country or region, it may be a sign that the system has been compromised. If your business is based in Los Angeles, seeing a user connecting to your network from another country with a bad reputation for international cybercrime is a cause for concern. Monitoring IP addresses on the network and their location can detect cyber attacks before they can damage your organization. Multiple connections to your accounts from unexpected locations could be a good indicator of compromise.

3. Unexplained Activity by Privileged User Accounts

In complex cyberattacks, such as advanced persistent threats, attackers often compromise low-privileged user accounts before escalating their privileges and authorizations. Security operators must watch for suspicious behavior from privileged user accounts, as this may be evidence of internal or external attacks on the organization’s systems.

4. Abnormal Account Behaviors

Anomalies in account behaviors aref, such as changes to login times, unusual access to files or databases, and failed login attempts, can indicate a data breach. Security personnel must monitor these behaviors to detect and prevent a potential security breach.

5. Abnormal File Modifications

Unexpected changes to system files or unauthorized software installation can signify a data breach. An attacker may use these modifications to gain control over the system or exfiltrate sensitive data. Trained personnel must keep track of these modifications and take action immediately if detected.

6. Communication With Known Malicious IPs

Attackers often use known malicious IPs to control the infected system or exfiltrate sensitive data. Security professionals must monitor communication with these IPs to detect and prevent a potential data breach.

7. Unauthorized Network Scans

Unauthorized network scans can signal a reconnaissance attack, where attackers try to gain information about the target network using open-source or propriety scanning tools.

8. Suspicious Files or Processes

Malware is often disguised as legitimate software, meaning malicious files and processes can be hidden in plain sight on your network. If you notice a suspicious file or process you do not recognize on your system, this could be a sign of an attack. It’s essential to investigate these files and processes thoroughly to determine their legitimacy.

9. Unusual System Behavior

Unusual System Behavior, such as unexpected restarts, crashes, or slow performance, can also be a sign of an IoC. Attackers may use denial-of-service attacks or resource exhaustion attacks to disrupt or bring down systems. If you notice any unexpected behavior from your systems, it’s essential to investigate and determine if there is a security threat.

10. Phishing Emails

Phishing emails are a common way for attackers to access sensitive information or install malware on a victim’s system. These emails can be challenging to spot, as they often appear to be legitimate communications from trusted sources. However, if you notice any suspicious emails, such as requests for login credentials or links to unfamiliar websites, it’s important to be cautious and investigate further.

11. Social Engineering Attempts

Social engineering attacks are another common tactic attackers use to access sensitive information. These attacks involve manipulating individuals to reveal sensitive information or perform actions that are not in their best interest. For example, an attacker may pose as a trusted source, such as a vendor or employee, to access sensitive data or install malware. It is essential to educate employees on the dangers of social engineering attacks and how to identify and avoid them.

12. Web Traffic Levels

Another common type of indicator of compromise is web traffic levels. If there is an unusual spike in web traffic to a particular website or IP address, it may be a sign that the system has been compromised. In addition, you should pay attention to unusual inbound and outbound network traffic, Domain Name Servers (DNS) requests and registry configurations, and an uptick in incorrect log-ins or access requests that may indicate brute force attacks.

13. DDoS Indicators

DDoS indicators detect and respond to distributed denial of service (DDoS) attacks. If an unusual amount of traffic comes from a particular IP address or range of IP addresses, it may be a sign that the system is under attack.

Why Are Indicators of Compromise (IoCs) Not Enough?

While understanding IoCs is essential, more than relying solely on technical indicators is required to detect advanced threats. Attackers are becoming more sophisticated in their approach and can easily evade traditional IoC detection methods. Therefore, a comprehensive approach to IoCs should also cover advanced threat detection techniques such as machine learning-based anomaly detection and behavioral analysis. Additionally, IoCs should not be considered in isolation but should be part of a broader threat intelligence program that includes information on the latest threat actors, tactics, and motivations. This approach can help organizations proactively detect and respond to threats before they occur.

Leveraging Indicators of Compromise

Organizations need to have a robust security strategy to leverage IoCs effectively. This strategy should include:

    1. Extended detection and response (XDR) – XDR enables organizations to collect, analyze, and correlate security data from multiple sources, including IoCs, to detect potential threats. Some organizations use Security Information and Event Management (SIEM) tools to get some of the coverage XDR can deliver.
    2. Endpoint Security Platforms – These platforms allow security teams to collect, search and enforce rules against IoCs.
    3. Threat Intelligence Platforms (TIPs) – TIPs provide organizations with access to curated threat intelligence feeds that include IoCs, enabling them to stay up-to-date on the latest threats.
    4. Incident Response Plans (IRPs) – Organizations should develop detailed IRPs that outline the steps to be taken in a security incident, including leveraging IoCs to detect and respond to potential threats.

IOCs Management Best Practices

If you want to manage IOCs effectively, there are several best practices you should follow:

  1. Prioritize Identity Security – Make sure you have a strong identity and access management controls in place. This will help you identify who has access to what and enable you to detect any unusual activity.
  2. Segment Networks – Segmenting your network can help limit the damage caused by a compromise. By separating critical systems from less important ones, you can reduce the likelihood of an attacker gaining access to sensitive information.
  3. Gather Cyber Threat Intelligence – Keep up-to-date with the latest cyber threats and trends. This will help you identify new threats and take action to mitigate them.
  4. Use IOC Tools – There are many tools available that can help you manage IOCs effectively. These include threat intelligence platforms, Extended detection and response, or XDR, systems, and endpoint detection and response (EDR) solutions.

One type of tool that is particularly useful for managing IOCs is an EDR (Endpoint Detection and Response) or XDR (Extended Detection and Response) solution. These solutions use a combination of advanced analytics, machine learning, and behavioral analysis to detect and respond to threats in real time.

Improve Cyber Security with SentinelOne

The most effective cybersecurity strategy combines human resources with advanced technological solutions, such as artificial intelligence (AI), machine learning (ML), and other forms of intelligent automation. These tools help detect abnormal activities and increase response and remediation time. If you’re looking for an EDR or XDR solution to help improve your cybersecurity, SentinelOne is an excellent choice. SentinelOne offers a comprehensive, AI-powered security platform that can help you detect and respond to threats quickly and effectively.


Indicators of Compromise (IoCs) are critical tools to help organizations detect and mitigate potential security incidents. By leveraging IoCs, organizations can detect threats quickly, monitor for future threats, improve incident response, and share threat intelligence with other organizations. However, to effectively leverage IoCs, organizations need a robust security strategy that includes XDR tools, TIPs, and detailed IRPs.

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