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I Scream, You Scream, We All Scream For IOCs

API Indicators of Compromise


APIs (Application Programming Interfaces) have become both invaluable assets and potential targets for cyber attacks. As these interfaces facilitate critical data exchange between different software applications, they also present unique vulnerabilities. 

Identifying Indicators of Compromise (IOCs) early is crucial in preventing and mitigating API attacks. IOCs are pieces of forensic data, such as system log entries or files, that identify potentially malicious activity on a system or network. This article explores 10 essential IOCs to monitor in API environments, complete with tangible examples.

1. Unusual API Traffic Patterns

Sudden spikes or unusual patterns in API usage can indicate a breach or abuse.

Example: Consider an e-commerce API that typically handles 1,000 requests per hour. If this suddenly spikes to 10,000 requests per hour without any promotional event or noticeable reason, it could signify an attempted breach or a DDoS attack.

2. Unauthorized API Requests

Requests from unknown or unauthorized sources, or an excessive number of failed authentication attempts.

Example: A financial services API starts receiving requests from unfamiliar user IDs or tokens, or there's a surge in failed authentication attempts. This can indicate unauthorized access attempts, possibly probing for vulnerabilities.

3. Suspicious IP Addresses

Traffic originating from IP addresses known for malicious activities or from geographically unusual locations.

Example: An educational platform's API receives requests from a high-risk IP address in a region where the platform has no student base.  

4. Anomalous Data Exfiltration

Unusually large data transfers or downloads that deviate from normal patterns.

Example: An API responsible for retrieving customer profiles suddenly logs a request that tries to download over 100TB of data, suggesting data exfiltration.

5. API Key Compromise Indicators

Repeated use of the same API key over short periods or from multiple locations.

Example: Observing repeated use of the same API key from vastly different geographic locations within a short time frame, suggesting the key might have been stolen and distributed.

6. Unusual System Behavior

Changes in system performance or functionality that might suggest backend manipulation through APIs.

Example: An API that usually processes requests within seconds starts showing delayed responses or frequent timeouts, hinting at potential backend tampering or resource exhaustion attacks.

7. Error Messages and System Logs

Frequent error responses from an API or unusual entries in system logs indicating attempted or successful unauthorized access.

Example: A notable increase in 'access denied' or 'unauthorized' error messages in an API’s server logs, pointing towards increased unauthorized access attempts.

8. Unusual Outbound Traffic

Traffic directed to unfamiliar external addresses, possibly indicating data being sent to an attacker’s server.

Example: Network monitoring tools detect unexpected data flow from the company's server to an unknown external server during API calls, which can be a sign of data being siphoned off.

9. Changes in File Integrity

Modifications to files or configurations that are not expected or authorized, especially in areas accessible via APIs.

Example: Modifications detected in API configuration files or scripts without any scheduled updates or administrative input, indicating possible tampering.

10. Compromised User Accounts

Activities from user accounts that show signs of being taken over, such as accessing APIs they normally don’t use or at odd hours.

Example: An account that usually accesses a particular API during business hours begins making requests late at night or starts executing atypical actions, suggesting a compromised account.


Recognizing these IOCs is vital for maintaining the integrity and security of APIs and the data they can access. Organizations must invest in monitoring and alert systems to detect these signs promptly. By doing so, organizations can preemptively identify and neutralize threats before they escalate. 


API I OC Infographic