Lernkarten

Karten 18 Karten
Lernende 0 Lernende
Sprache English
Stufe Universität
Erstellt / Aktualisiert 19.06.2019 / 19.06.2019
Lizenzierung Keine Angabe
Weblink
Einbinden
0 Exakte Antworten 18 Text Antworten 0 Multiple Choice Antworten

1/18

Fenster schliessen

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.
Fenster schliessen

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.
Fenster schliessen

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.

Fenster schliessen

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
Fenster schliessen

Name some network based IOCs.

Network based IOCs

  • IPs addresses or domain of CC
  • CC protocol characteristics
  • WHIOIS information
Fenster schliessen

What is Yara?

Yara is a language to check for IOCs

  • open language anyone can write rules
  • allows shareing of rules
Fenster schliessen

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
Lizenzierung: Keine Angabe
Fenster schliessen

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
Fenster schliessen

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.

Fenster schliessen

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
Fenster schliessen

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
Fenster schliessen

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
Fenster schliessen

What is packing and why is it done by malware?

Lizenzierung: Keine Angabe

Packing is an ovfuscation technique used by malware, with two goals:

  • Evading AV signatures
  • Prevent or slow down static analysis
Fenster schliessen

How can you unpack malware?

To unpack malware it is often sufficient to dump memory of the unpacked process, recieving memory injections.

Fenster schliessen

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

Fenster schliessen

What can virustotal be used for?

https://www.virustotal.com/gui/home/upload

we can upload dll and executables that we extracted with dlldump and procdump to malfind for automatic analysis.

Fenster schliessen

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.

Fenster schliessen

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