Skip to main content

Posts

Showing posts from August, 2009

Welcome to Mark Baggett - In Depth Defense



I am the course Author of SANS SEC573 Automating Information Security with Python. Check back frequently for updated tools and articles related to course material.

Senior SANS Instructor
GSE #15
Internet Storm Center Handler
Penetration Testing and Incident Response Consultant
Technical Advisor to DoD for The SANS Institute
Founding President of the Greater Augusta ISSA
Cofounder of BSidesAugusta Security Conference


Tools:
FREQ SERVER - Tool and technique for detecting Malware Command and Control domains
DOMAIN_STATES - Tool for detecting "Baby Domains" used for phishing and Malware distribution
SRUM_DUMP - Forensics tool for extracting System Resource Utilization Monitoring artifacts
LIAM_NEESON - Proof of Concept Linux Hash Protection
HONEY_HASHES - Certainly Honey Tokens have been around since 2003 but I created a cool technique for creating fake SATs in memory that was turned into Dell Secure Works DCEPT framework.
VSSOWN - Tool & Technique for Using Microsoft Volume Shadow Copies for hiding malware and extracting artifacts
SDB Hacking - Using Application Compatibility in unexpected ways.
SET-KBLED - Utility for Managing Clevo and Sager Laptop LED Backlit Keyboards
Reassembler.py - Scapy based fragement reassembly engine
eapmd5crack.py - A password cracker for the EAP protocol


and more. Most of these tools are available on my github page. Follow me on twitter @markbaggett





TCP Fragment Evasion

Originally posted on http://pauldotcom.com/2009/08/tcp-frament-evasion-attacks.html

By: Mark Baggett

I recently read a very good article on tuning Snort's Stream5 preprocessor to avoid "TCP Fragment Overlap" attacks. It's a great article, but the wording confused me. I thought to myself, "TCP Fragments, that must be a mistake. The TCP Header doesn't have a 'more fragments bit', a 'fragment offset' or anything to support fragmentation. How can there be any TCP fragments?"   Typically when we talk about fragmentation attacks we think about Layer 3 attacks. Attackers manipulate the IP packet headers to pull off various insertion and evasion attacks. Examples of layer3 attacks include overlapping fragment attacks and temporal evasion (host reassembly timeout evasion). These attacks are explained pretty well in an article titled "Evading NIDS, revisited".
So what is TCP or Layer 4 "fragmentation"? Really, its overl…