Top 7 Log Sources Every SOC Analyst Should Know

For a Security Operations Center (SOC) Analyst, information is the most potent tool, arriving in the form of raw logs. These digital traces tell the complete story of every action, connection, and unusual event happening in an environment. To effectively detect, analyze, and respond to cyber incidents, an Analyst must thoroughly understand the origin of these crucial logs. By mastering these seven essential log sources, Analysts can proactively identify and respond to threats quickly when issues arise.

Top 7 Log Sources Every SOC Analyst Should Know

1. Windows Event Logs

Windows Event Logs give SOC Analysts vital clues about what’s happening on Windows computers, whether they’re servers or desktops. To truly understand these logs, Analysts must know the meaning of specific event IDs.

• Logon Events: Analysts carefully review these logs to identify who is attempting to log in and whether the attempt is successful or unsuccessful (such as Event ID 4624 for a successful login and 4625 for an unsuccessful one). A large number of failed logins from a single location or multiple accounts can alert Analysts to potential brute-force attacks or credential stuffing.
• Process Creation: By monitoring process creation (Event ID 4688), Analysts can identify unusual programs running, odd commands, or processes that other programs shouldn’t initiate. These are all signs of malware or unauthorized activity.
• Network Access: Events related to network connections indicate who is communicating with whom. Analysts can identify rogue connections or unusual traffic flows, which may indicate command-and-control (C2) communication or unauthorized data extraction.

2. Firewall Logs

Firewall logs are essential for understanding what’s happening at your network’s edge; they serve as your first line of defense.

• Blocked Connections: Analysts review these logs to identify attempts to access unauthorized services or ports. Many blocks from the same external computer can indicate someone conducting reconnaissance (spying) or even targeted attacks.
• Port Scans: Firewall logs frequently show port scanning, which is when attackers “knock on all doors” to find open ones. Spotting these patterns helps Analysts identify who is trying to map your network’s weaknesses.

3. Endpoint Security Logs

Endpoint Detection and Response (EDR) tools, as well as traditional antivirus (AV) programs, provide a highly detailed view of what is happening on individual computers and devices.

• Malware Alerts: When your AV or EDR flags something like a malware, a virus, or even just unwanted software, the Analysts take immediate action. They quickly investigate these alerts because understanding the “why” and “how” behind them is key to truly fixing the problem.
• EDR Detections: EDR logs are like a treasure trove of information! They display everything from the programs running to changes in files and even network connections directly from a device. Analysts examine this data to identify advanced threats, piece together how an attack occurred, and assess the extent of the damage caused by a breach.

4. Web Server Logs

Web server logs record every single interaction with your websites and online applications. They’re like a diary that reveals sneaky attacks targeting these crucial parts of your business.

• Access Patterns: Analysts review these logs, looking for anything out of the ordinary – such as a sudden surge in traffic, users accessing pages too quickly, or behavior that doesn’t appear to be that of a regular user. These can be red flags for automated attacks or even someone scraping your website’s content.
• 404 Errors (Not Found): If you encounter numerous “page not found” errors, especially for web addresses that don’t exist but are common hacking targets (such as attempts to access, administer, or login), that’s a strong indication of reconnaissance (spying) or vulnerability scanning. Attackers are poking around to find weak spots.
• Injections: Hints of malicious tricks, such as SQL injection (attempting to compromise your database) or Cross-Site Scripting (XSS), often appear as unusual characters or suspicious commands embedded in the web address or form data. Analysts recognize these as signs of someone attempting to inject malicious code.

5. VPN Logs

As many of us now work remotely, VPN logs are essential for monitoring connections and identifying any anomalies.

• Remote Access Anomalies: Analysts search for unusual login times, connections from unexpected locations, or multiple people logging into the same user account simultaneously. These are significant clues that someone might have stolen login details.
• Failed Login Attempts: A sudden spike in failed VPN logins can indicate that someone is attempting to brute-force their way into your remote access systems.

6. DNS Logs

DNS (Domain Name System) logs records every time someone asks for a website’s address, making them a goldmine for spotting threats.

• Domain Abuse: Analysts look for requests to websites known to be malicious – such as phishing sites or those hosting malware – often flagged by their threat intelligence.
• C2 Callbacks: DNS is a favorite way for malware to “talk back” to its controllers. Analysts look for unusual, repeated, or persistent requests to suspicious websites, which may indicate the presence of active malware on the network.

7. Proxy Logs

Proxy logs provide Analysts with a detailed play-by-play of what everyone inside the network is browsing online and how well the web filters are working.

• Web Traffic: Analysts review these logs to understand what users are viewing, identify visits to unapproved or questionable websites, and ensure compliance with the rules.
• Filtering Evasion: If logs indicate that users are attempting to bypass the proxy or access blocked websites, this is a key sign of either risky user behavior or active malware trying to establish a connection.

SOC Analyst Hands-on Training with InfosecTrain

Mastering these log sources enables SOC Analysts to detect threats early, respond more quickly, and significantly reduce organizational risk. Make log analysis a daily habit and fine-tune alerts, as logs always tell a story that an Analyst must interpret. As cyber threats grow, InfosecTrain’s SOC Analyst training course effectively bridges critical skills gaps, covering SIEM, malware analysis, and digital forensics. This hands-on program equips participants with practical expertise to detect, analyze, and respond to complex cyber incidents. Investing in such training is crucial for building a resilient defense against today’s sophisticated cyber adversaries.

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