In the realm of cybersecurity, incident response (IR) is a critical function that helps organizations detect, mitigate, and recover from security incidents. A robust incident response strategy requires access to various logs and data sources, which provide insights into potentially malicious activities.
Key Logs for Incident Response
When responding to an incident, one of the first steps is to gather logs for egress connections. These logs are vital because they serve as filter points for all traffic leaving the environment, helping to identify command and control (C2) points and compromised internal systems. The primary sources of egress connection logs include:
Firewall Logs: These logs capture all outbound connections, providing a comprehensive view of egress traffic. Firewalls are configured to monitor and control the flow of network traffic based on predetermined security rules.
DNS Logs: DNS logs are powerful tools for detecting malicious traffic. They can reveal domains and IP addresses associated with known malware and botnets. Comparing DNS logs with known bad domain lists can quickly highlight potential threats.
Web-Filtering Device Logs: Web proxies and content filters restrict access to objectionable content and can detect malicious outbound traffic. These logs help identify access to known bad domains and suspiciously long URLs used by malware for C2 or payload delivery.
The Power of DNS Data
DNS data can be instrumental in detecting malicious activities within an environment. Traditional antivirus solutions may fail to detect certain well-known malicious programs, but DNS logs can still reveal their presence. Here are some reasons why DNS data is so valuable:
Static Domains: Many botnets and C2 channels use relatively static domains, making it easier to track them through DNS logs.
Comparison with Blacklists: Tools like dns-blacklists.py allow responders to compare DNS server caches with lists of known malicious IPs and domains, such as those provided by Malware Domain List. This helps quickly identify compromised systems.
Utilizing Web Proxy Content Filters
Most enterprises deploy web proxy content filters to manage and restrict employee access to various websites. These devices are not only useful for enforcing internet usage policies but also serve as potent tools during incident response. Here’s how:
Identifying Known Bad Actors: Web proxy logs can be checked against updated blacklists to identify access to known malicious IPs and domains.
Analyzing URL Lengths: Malware often uses long, encoded URLs for C2 communication or payload delivery. While legitimate sites also use long URLs, combining this indicator with other signs of compromise can be effective.
Reviewing User Agent Strings: Anomalies in user agent strings, such as outdated versions or unexpected operating systems, can indicate the presence of malware.
Detecting Beaconing Activity
Modern malware often uses intermittent beaconing to communicate with C2 servers, rather than maintaining a persistent connection. Detecting this type of activity requires analyzing connection logs from egress firewalls that perform Network Address Translation (NAT). Regular or irregular intervals in outbound connections can indicate beaconing behavior.
Pulling Data from Multiple Systems
In an enterprise environment, gathering data from multiple systems simultaneously is crucial for a comprehensive incident response. The Windows Management Instrumentation Command-line (WMIC) tool can be used to collect software inventory across multiple systems efficiently. Here’s an example command:
C:\> wmic /node:@systems.txt product get name, version, vendor /format:csv > SoftwareInventory.txtThis command retrieves the software inventory from all systems listed in systems.txt, providing a detailed overview of installed software, which is essential for identifying vulnerable or unauthorized applications.
Conclusion
Effective incident response relies on leveraging various data sources to detect and mitigate threats. By utilizing firewall logs, DNS logs, and web-filtering device logs, responders can gain critical insights into malicious activities.
Akash Patel
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