Cyber Threats and Log Evasion: How Attackers Avoid Firewall Logging

Cyber threats are changing every day, and one of the most clever strategies attackers use is log evasion. If you take care of the firewall security of your workplace, it is important to know how hackers avoid firewall logging. Let’s get to the bottom of a few of these common tactics attackers utilize. More important, let’s get a sense for how you and I can stop them. This blog unpacks the tricks — and the defenses — in plain speak. Ready? Let’s go.

1. Log Tampering Techniques

Log tampering is one of the oldest tricks in the book. Now imagine that somebody came along and sneakily deleted or changed the records of what they did — scary, no? Attackers try to:

• Erase suspicious entries to hide their tracks.
• Timestamp alteration so that events appear to have occurred at different times.
• Insert false logs to mislead administrators.

Hackers tend to target systems that log activity locally or have only minimal monitoring in place. They take advantage of weak permissions or software vulnerabilities that have given them write access to the logs.

To stop this:

• Centralized logging, so logs are sent to a different (safe) server.
• Make logs read-only so that no one can alter it.
• Create alerts when logs are deleted or modified.
• Automate firewall log audit.

If you allow attackers to mop around your logs, you won’t see them coming next time.

2. Stealthy Malware Traffic

Not all bad traffic is obviously bad traffic. Malware today knows how to disguise itself. They may operate with low bandwidth, do things at random times, or fake legitimate protocols in order to slip past firewalls undetected. Here’s where attackers get sneaky:

• Port hop, or use non-standard ports so you don’t see the common suspects.
• They can mask malware communication as regular web traffic, or through popular services.
• Exfiltrate data little by little over a long period of time.
• Use polymorphic malware that randomizes appearance.

For firewall security people like you and me, detection of this stealth traffic is challenging but possible:

• You need to see off-pattern traffic over time and not just one big spike.
• Deploy deep packet inspection to see what’s going on inside the packets.
• Employ behavioral analytics that identify anomalies from the norm.
• Use threat intelligence feeds and keep malware signatures up to date.

The mission is to detect the telltale signals before the harm is done.

3. Abuse Of Privilege Listing & Covert Attacks

Not all assailants are the foreign enemy. Occasionally, as an employee in your organization, somebody quietly jacks around with firewall logs or sneaks past detection. Insider threats are challenging because they are often legitimately vested. Common tactics include:

• Temporary or permanent logging disabling.
• Using valid credentials to perform silent malicious activity.
• Leveraging their understanding of firewall regras to remain undetected.

How to safeguard insiders from trying to cover their tracks?

• Implement stringent access control and role-based permissions.
• Enable multi-factor authentication for administrators.
• Continuously monitor user behavior with anomaly detection.
• Maintain an immutable audit trail of activity by insiders.

Insiders have an advantage, but controls can equalize it.

4. Encryption to Evade Detection

Attackers love encryption because it obfuscates their evil payloads. When traffic is encrypted entirely, so you can’t easily peer into logs with traditional firewalls, you create blind spots.

Here’s what hackers do:

• Embed malicious traffic in SSL/TLS connections so it appears normal.
• Use VPNs or proxies to conceal their actual endpoints.
• Use custom encrypted protocols that may not be comprehensible to firewall logs.

To counter this:

• Use SSL/TLS inspection (sometimes called HTTPS decryption) judiciously.
• Deploy next-gen firewalls with integrated functionalities to analyze encrypted traffic.
• Augment with endpoint detection and response (EDR) for indicators of compromise beyond the firewall log.
• Educate your team members to identify signs when encrypted channels are being misused.

Encryption can protect you, but unfortunately that is how attackers also protect themselves.

5. Strengthening Log Integrity

If logs are your window into attacks, they need to be trusted. Here’s what we need to do to make sure:

• Use tamper-resistant systems to centralize and aggregate logs.
• Use WORM (or write once read many) storage or immutable logs.
• Use cryptography (hashing and digital signatures) to verify logs.
• Deploy alerting tools that are automated to detect abnormal log behaviors.
• Regular penetration testing and audits to test your defenses.

When you make your logs bulletproof, you gain the ability to make an attacker shed a layer then they start attempting to harm you.

In Summary

Cyber threats are intelligent and very adaptive. To bypass firewalls, attackers employ log evasion, stealth attacks, insider tricks, and encryption. But with vigilance, smart tools and solid practices, you can lock down firewall security and ensure your logs are clean and reliable. Keep a leg up — jack up on your steps and protect like a boss. Your business depends on it.