Anti-forensics
The term "anti-forensics" is used sometimes to describe efforts attackers use in order to foil or frustrate the attempts of the good guys to discover what happened, when it happened, and how it happened. Many times, what comes to mind when someone uses the term "anti-forensics" are things like steganography, rootkits, and timestomp.
Richard Bejtlich went so far as to make a distinction between the terms "anti-forensics" and "counterforensics". On Wikipedia, the term "anti-computer forensics" is used to refer tocountermeasures against forensic analysis, while "counterforensics" refers to attacks directed against forensic tools. For additional clarification on the terms, see W. Matthew Hartley's paper on the topic here; the paper is three pages long, and makes a clear distinction between the two terms.
In short, from Hartley's paper, anti-forensics refers to techniques and technologies that "invalidate factual information for judicial review", whereas counterforensics refers to tools and techniques that "target...specific forensic technologies to directly prevent the investigator from analyzing collected evidence". Hartley's paper gives some very good examples to illustrate the differences between these two terms, so I strongly suggest reading the three pages.
Very often, we use these terms (in some manner) to describe what an attacker or intruder may do, but one thing that's not discussed often is how this applies to responder's actions, or inaction, as the case may be. In that regard, there are a couple of things that organizations and responders need to keep in mind:
1. You can not just grab the disk and expect to get what you need. Live response, including memory acquisition, is becoming more and more important, particularly in the face of questions brought on by legislative and regulatory compliance. Too many times, a response team (consultants, not on-site staff) will be called in and during the course of response, but provided with goals. Then, after the fact, the victim organization will start with questions such as, "...was data exfiltrated?" and "...how much data was exfiltrated?" Fortunately, consulting responders have faced these questions often enough that they can often head them off at the pass, but what do you do when the victim organization has already taken systems offline before calling for help? Would it have been beneficial to the overall response if they'd captured memory, and perhaps some volatile data, first?
2. Temporal Proximity - lots of stuff happens on Windows systems, particularly since Windows XP was released, that have an antiforensics effect...and much of it happens without any interaction from a user or administrator. Let's say that a bad guy gets into a system, uploads a couple of tools, runs them, copies data off of the system, then deletes everything and leaves. While the system is just sitting there, there are limited defrags going on, System Restore Points and Volume Shadow Copies are being created and removed, operating system and application updates are being installed, etc. It won't be long before, due to a lack of responsiveness, all you're left with is an entry in an index file pointing to a file name. Once that happens, and you're unable to determine how many records were exposed, you will very likely have to report and notify on ALL records. Ouch!
The point is that intruders very often don't have to use any fancy or sophisticated techniques to remain undetected on a system or within a network infrastructure. What tends to happen is that responders and analysts may have only so much time (8 hrs, 16 hrs, etc.) to spend on investigating the incident, so as long as the intruder uses a technique that takes just a bit longer than that to investigate, they're good. There's no real need to use counter- or anti-forensics techniques. Very often, though, it's not so much the actions of the intruder, but the inaction of the closest responders that have the greatest impact on an investigation.
Thoughts?
Resources
Anti-forensics.com
Antiforensics.net
ForensicsWiki: Anti-forensics
Adrien's Occult Computing presentation
CSOOnline article: The Rise of Anti-Forensics
Lance Mueller: Detecting Timestamp Changing Utilities
Richard Bejtlich went so far as to make a distinction between the terms "anti-forensics" and "counterforensics". On Wikipedia, the term "anti-computer forensics" is used to refer tocountermeasures against forensic analysis, while "counterforensics" refers to attacks directed against forensic tools. For additional clarification on the terms, see W. Matthew Hartley's paper on the topic here; the paper is three pages long, and makes a clear distinction between the two terms.
In short, from Hartley's paper, anti-forensics refers to techniques and technologies that "invalidate factual information for judicial review", whereas counterforensics refers to tools and techniques that "target...specific forensic technologies to directly prevent the investigator from analyzing collected evidence". Hartley's paper gives some very good examples to illustrate the differences between these two terms, so I strongly suggest reading the three pages.
Very often, we use these terms (in some manner) to describe what an attacker or intruder may do, but one thing that's not discussed often is how this applies to responder's actions, or inaction, as the case may be. In that regard, there are a couple of things that organizations and responders need to keep in mind:
1. You can not just grab the disk and expect to get what you need. Live response, including memory acquisition, is becoming more and more important, particularly in the face of questions brought on by legislative and regulatory compliance. Too many times, a response team (consultants, not on-site staff) will be called in and during the course of response, but provided with goals. Then, after the fact, the victim organization will start with questions such as, "...was data exfiltrated?" and "...how much data was exfiltrated?" Fortunately, consulting responders have faced these questions often enough that they can often head them off at the pass, but what do you do when the victim organization has already taken systems offline before calling for help? Would it have been beneficial to the overall response if they'd captured memory, and perhaps some volatile data, first?
2. Temporal Proximity - lots of stuff happens on Windows systems, particularly since Windows XP was released, that have an antiforensics effect...and much of it happens without any interaction from a user or administrator. Let's say that a bad guy gets into a system, uploads a couple of tools, runs them, copies data off of the system, then deletes everything and leaves. While the system is just sitting there, there are limited defrags going on, System Restore Points and Volume Shadow Copies are being created and removed, operating system and application updates are being installed, etc. It won't be long before, due to a lack of responsiveness, all you're left with is an entry in an index file pointing to a file name. Once that happens, and you're unable to determine how many records were exposed, you will very likely have to report and notify on ALL records. Ouch!
The point is that intruders very often don't have to use any fancy or sophisticated techniques to remain undetected on a system or within a network infrastructure. What tends to happen is that responders and analysts may have only so much time (8 hrs, 16 hrs, etc.) to spend on investigating the incident, so as long as the intruder uses a technique that takes just a bit longer than that to investigate, they're good. There's no real need to use counter- or anti-forensics techniques. Very often, though, it's not so much the actions of the intruder, but the inaction of the closest responders that have the greatest impact on an investigation.
Thoughts?
Resources
Anti-forensics.com
Antiforensics.net
ForensicsWiki: Anti-forensics
Adrien's Occult Computing presentation
CSOOnline article: The Rise of Anti-Forensics
Lance Mueller: Detecting Timestamp Changing Utilities