Bangeter 04-malware_identification_v50.pdf
Bangeter 04-malware_identification_v50.pdf
Bangeter 04-malware_identification_v50.pdf
Fichier Détails
| Cartes-fiches | 18 |
|---|---|
| Langue | English |
| Catégorie | Technique |
| Niveau | Université |
| Crée / Actualisé | 19.06.2019 / 01.07.2021 |
| Lien de web |
https://card2brain.ch/box/20190619_bangeter_04malwareidentificationv50_pdf
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Why is malware identification important?
- Malware identification is important for incident reponse in a company or in law enforcement context.
- In cyber crime case: reinstall machine and you're done.
- Espionage type of attack possible affects substantial parts of a network and requiers different / more complex reactions.
How can malware identification help us in our analysis of the malware?
- Mostly the same attack has been used befor.
- Most malware families have been analyzed befor -> addition information
- Through identifying malware we emidiatly get access to all work done previously
- analysis of new malware can take days to months.
What is an IOC (Indicator of Compromise)?
An indicator of compromise (IOC) is an a priori known characteristic artefact of attacks, malware samples / families.
IOCs can be used for detection and identification purposes.
Name some host based IOCs (Indicator of Compromise)
Host based IOCs
- Hashes of malware executables, modules, dropped files etc...
- Filenames of dropped files or email attachements (infection vector)
- Registry entries (e.g. used for persistence)
- Mutexes (program object that is created so that multiple program thread can take turns sharing the same resource, such as access to a file.)
- Process names
- Anti-virus or Yara signatures
- Strings
Name some network based IOCs.
Network based IOCs
- IPs addresses or domain of CC
- CC protocol characteristics
- WHIOIS information
What is Yara?
Yara is a language to check for IOCs
- open language anyone can write rules
- allows shareing of rules
How difficult is it for an attacker to change the IOCs of following components:
- TTPs (Tactics, Techniques and Procedures)
- Tools
- Network /Host Artifacts
- Domain Names
- IP Addresses
- Hash Values
What is an advantage of yarea rules and for what purposes can they be used?
In contrast to AV engine rules, Yara rules can be written and shared by anybody, which allows security teams to act independently of vendors.
Yara rules ca be used in different places of an organiyation's detection / security technologies:
- Memory forensic investigation
- Sandboxes
- Endpoint / AV
- Gateway detection
Why does the manual malware analysis not scale well, what can be doen?
Malware analysis can be very time consuming and expensive. Shortage of skilled analysts and an abundant number of malware samples does not scale well
Solution: Analysis automation
AV vendors and threat intelligence companies automatically process and analyze feeds of 100'000s of malware samples per day to generate, better av signatures IOCs or threat intelligence.
What are malware sandboxes and what are they used for?
Malware sandboxes automate malware (binaries, documents, URLs) analysis, and typically allow to quickly:
- Determin whether a sampe is malicious
- Determine IOCs
- Determine the malware family (in some cases), e.g. based on correlation of IOCs or using Yara rules
Malsware sandboxes are dynamic analysis systems:
- Samples submitted to a sandox are executed for a couple of minutes
- Then an analysis report is presented to the user.
- Analysis reports can often be read by less skillec analysts for triage purposes
How can dynamic analysis techniques be defeated by malware (Anti analysis)
- Detection of the instruments being used
- Detection of debuggers, or prevent attaching debuggers
- Detecting virtual machines
- Malware sleeps for a couple of minutes to defeat sandboxes
- Malware tries to figure out whether it is on a real machine or running in a Sandbox:
- No user interaction
- Small memory of analysis machine
- Only one CPU
- etc...
- Once an analysis environmment is detected, malware will exit, or show non-malicious behavior
what is the differnce of PE files on disk vs. in memory, and what are the implications of that?
In general it is impossible to recontruct the original PE file from memory since some modifications cannot be undone:
- IAT
- Relocations
- Some pages may be missing from memory
Don't expect the recovered PE files to be runnable
Recovered PE files are sufficent for analysis with IDA Pro or to upload to Virustotal.
Malware sometimes modifies /destructs the PE header in memory to make reconstruction hard/impossible
PE files in memory contains more information than PE files on disk:
- DLLs used by PE file
- Dynamic data such as heap and stack
What is packing and why is it done by malware?
Packing is an ovfuscation technique used by malware, with two goals:
- Evading AV signatures
- Prevent or slow down static analysis
How can you unpack malware?
To unpack malware it is often sufficient to dump memory of the unpacked process, recieving memory injections.
What volatility commands can be used for memory extraction?
PE rebuild
- prcdump
- dlldump
Raw:
- vaddump
- memdump
- malfind ... ./dumps-malfind
General limitation: Memory that is paged out cannot be dumped, which can result in corruption when dumping PE files
What can virustotal be used for?
we can upload dll and executables that we extracted with dlldump and procdump to malfind for automatic analysis.
Why is it important to extract and analyze strings from processes / binaries?
The dumped strings may contain:
- CC commands
- CC URLs
- Filesystem paths
- Malware names
- Names of AVs to kill
- Malware log messages
- ...
In some cases, the strings may be sufficient to identify a sample, or at least to develop a first understanding of a samples capabilities.
How can strings be extracted from processes and binaries?
Simply run strings on dumped (and unpacked) process memory, DLLs ,etc..
Under linux two invocations of strings needs to be made for ASCII and unicode strings
strings -el memory.bin
stings memory.bin
