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Yara

Install

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sudo apt-get install -y yara
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Prepare rules

Use this script to download and merge all the yara malware rules from github: https://gist.github.com/andreafortuna/29c6ea48adf3d45a979a78763cdc7ce9 Create the rules directory and execute it. This will create a file called malware_rules.yar which contains all the yara rules for malware.
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wget https://gist.githubusercontent.com/andreafortuna/29c6ea48adf3d45a979a78763cdc7ce9/raw/4ec711d37f1b428b63bed1f786b26a0654aa2f31/malware_yara_rules.py
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mkdir rules
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python malware_yara_rules.py
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Scan

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yara -w malware_rules.yar image #Scan 1 file
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yara -w malware_rules.yar folder #Scan hole fodler
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YaraGen: Check for malware and Create rules

You can use the tool YaraGen to generate yara rules from a binary. Checkout these tutorials: Part 1, Part 2, Part 3
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python3 yarGen.py --update
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python3.exe yarGen.py --excludegood -m ../../mals/
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ClamAV

Install

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sudo apt-get install -y clamav
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Scan

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sudo freshclam #Update rules
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clamscan filepath #Scan 1 file
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clamscan folderpath #Scan the hole folder
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IOCs

IOC means Indicator Of Compromise. An IOC is a set of conditions that identifies some potentially unwanted software or a confirmed malware. Blue Teams use this kind of definitions to search for this kind of malicious files in their systems and networks. To share these definitions is very useful as when a malware is identified in a computer and an IOC for that malware is created, other Blue Teams can use it to identify the malware faster.
A tool to create or modify IOCs is IOC Editor. You can use tools such as Redline to search for defined IOCs in a device.

Loki

Loki is a scanner for Simple Indicators of Compromise. Detection is based on four detection methods:
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1. File Name IOC
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Regex match on full file path/name
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2. Yara Rule Check
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Yara signature match on file data and process memory
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3. Hash Check
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Compares known malicious hashes (MD5, SHA1, SHA256) with scanned files
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4. C2 Back Connect Check
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Compares process connection endpoints with C2 IOCs (new since version v.10)
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Linux Malware Detect

Linux Malware Detect (LMD) is a malware scanner for Linux released under the GNU GPLv2 license, that is designed around the threats faced in shared hosted environments. It uses threat data from network edge intrusion detection systems to extract malware that is actively being used in attacks and generates signatures for detection. In addition, threat data is also derived from user submissions with the LMD checkout feature and from malware community resources.

rkhunter

Tools like rkhunter can be used to check the filesystem for possible rootkits and malware.
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sudo ./rkhunter --check -r / -l /tmp/rkhunter.log [--report-warnings-only] [--skip-keypress]
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PEpper

PEpper checks some basic stuff inside the executable (binary data, entropy, URLs and IPs, some yara rules).

NeoPI

NeoPI is a Python script that uses a variety of statistical methods to detect obfuscated and encrypted content within text/script files. The intended purpose of NeoPI is to aid in the detection of hidden web shell code.

php-malware-finder

PHP-malware-finder does its very best to detect obfuscated/dodgy code as well as files using PHP functions often used in malwares/webshells.

Apple Binary Signatures

When checking some malware sample you should always check the signature of the binary as the developer that signed it may be already related with malware.
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#Get signer
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codesign -vv -d /bin/ls 2>&1 | grep -E "Authority|TeamIdentifier"
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#Check if the app’s contents have been modified
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codesign --verify --verbose /Applications/Safari.app
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#Check if the signature is valid
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spctl --assess --verbose /Applications/Safari.app
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Detection Techniques

File Stacking

If you know that some folder containing the files of a web server was last updated in some date. Check the date all the files in the web server were created and modified and if any date is suspicious, check that file.

Baselines

If the files of a folder shouldn't have been modified, you can calculate the hash of the original files of the folder and compare them with the current ones. Anything modified will be suspicious.

Statistical Analysis

When the information is saved in logs you can check statistics like how many times each file of a web server was accessed as a webshell might be one of the most.
Last modified 1mo ago