القائمة
Examine Linux system artifacts including auth logs, cron jobs, shell history, and system configuration to uncover evidence of compromise or unauthorized activity.
التثبيت باستخدام Codex أو Claude انسخ هذا Prompt والصقه في Codex أو Claude أو مساعد آخر ليراجع صفحة Skill ويثبّتها لك.
استنادا إلى تصنيف SOC المهني
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| name | analyzing-linux-system-artifacts |
| description | Examine Linux system artifacts including auth logs, cron jobs, shell history, and system configuration to uncover evidence of compromise or unauthorized activity. |
# Mount forensic image read-only
mount -o ro,loop,offset=$((2048*512)) /cases/case-2024-001/images/linux_evidence.dd /mnt/evidence
# Create collection directories
mkdir -p /cases/case-2024-001/linux/{logs,config,users,persistence,network}
# Collect authentication logs
cp /mnt/evidence/var/log/auth.log* /cases/case-2024-001/linux/logs/
cp /mnt/evidence/var/log/secure* /cases/case-2024-001/linux/logs/
cp /mnt/evidence/var/log/syslog* /cases/case-2024-001/linux/logs/
cp /mnt/evidence/var/log/kern.log* /cases/case-2024-001/linux/logs/
cp /mnt/evidence/var/log/audit/audit.log* /cases/case-2024-001/linux/logs/
cp /mnt/evidence/var/log/wtmp /cases/case-2024-001/linux/logs/
cp /mnt/evidence/var/log/btmp /cases/case-2024-001/linux/logs/
cp /mnt/evidence/var/log/lastlog /cases/case-2024-001/linux/logs/
cp /mnt/evidence/var/log/faillog /cases/case-2024-001/linux/logs/
# Collect user artifacts
for user_dir in /mnt/evidence/home/*/; do
username=$(basename "$user_dir")
mkdir -p /cases/case-2024-001/linux/users/$username
cp "$user_dir"/.bash_history /cases/case-2024-001/linux/users/$username/ 2>/dev/null
cp "$user_dir"/.zsh_history /cases/case-2024-001/linux/users/$username/ 2>/dev/null
cp -r "$user_dir"/.ssh/ /cases/case-2024-001/linux/users/$username/ 2>/dev/null
cp "$user_dir"/.bashrc /cases/case-2024-001/linux/users/$username/ 2>/dev/null
cp "$user_dir"/.profile /cases/case-2024-001/linux/users/$username/ 2>/dev/null
cp "$user_dir"/.viminfo /cases/case-2024-001/linux/users/$username/ 2>/dev/null
cp "$user_dir"/.wget-hsts /cases/case-2024-001/linux/users/$username/ 2>/dev/null
cp "$user_dir"/.python_history /cases/case-2024-001/linux/users/$username/ 2>/dev/null
done
# Collect root user artifacts
cp /mnt/evidence/root/.bash_history /cases/case-2024-001/linux/users/root/ 2>/dev/null
cp -r /mnt/evidence/root/.ssh/ /cases/case-2024-001/linux/users/root/ 2>/dev/null
# Collect system configuration
cp /mnt/evidence/etc/passwd /cases/case-2024-001/linux/config/
cp /mnt/evidence/etc/shadow /cases/case-2024-001/linux/config/
cp /mnt/evidence/etc/group /cases/case-2024-001/linux/config/
cp /mnt/evidence/etc/sudoers /cases/case-2024-001/linux/config/
cp -r /mnt/evidence/etc/sudoers.d/ /cases/case-2024-001/linux/config/
cp /mnt/evidence/etc/hosts /cases/case-2024-001/linux/config/
cp /mnt/evidence/etc/resolv.conf /cases/case-2024-001/linux/config/
cp -r /mnt/evidence/etc/ssh/ /cases/case-2024-001/linux/config/
# Analyze user accounts for anomalies
python3 << 'PYEOF'
print("=== USER ACCOUNT ANALYSIS ===\n")
# Parse /etc/passwd
with open('/cases/case-2024-001/linux/config/passwd') as f:
for line in f:
parts = line.strip().split(':')
if len(parts) >= 7:
username, _, uid, gid, comment, home, shell = parts[0], parts[1], int(parts[2]), int(parts[3]), parts[4], parts[5], parts[6]
# Flag accounts with UID 0 (root equivalent)
if uid == 0 and username != 'root':
print(f" ALERT: UID 0 account: {username} (shell: {shell})")
# Flag accounts with login shells that shouldn't have them
if shell not in ('/bin/false', '/usr/sbin/nologin', '/bin/sync') and uid >= 1000:
print(f" User: {username} (UID:{uid}, Shell:{shell}, Home:{home})")
# Flag system accounts with login shells
if uid < 1000 and uid > 0 and shell in ('/bin/bash', '/bin/sh', '/bin/zsh'):
print(f" WARNING: System account with shell: {username} (UID:{uid}, Shell:{shell})")
# Parse /etc/shadow for account status
print("\n=== PASSWORD STATUS ===")
with open('/cases/case-2024-001/linux/config/shadow') as f:
for line in f:
parts = line.strip().split(':')
if len(parts) >= 3:
username = parts[0]
pwd_hash = parts[1]
last_change = parts[2]
if pwd_hash and pwd_hash not in ('*', '!', '!!', ''):
hash_type = 'Unknown'
if pwd_hash.startswith('$6$'): hash_type = 'SHA-512'
elif pwd_hash.startswith('$5$'): hash_type = 'SHA-256'
elif pwd_hash.startswith('$y$'): hash_type = 'yescrypt'
elif pwd_hash.startswith('$1$'): hash_type = 'MD5 (WEAK)'
print(f" {username}: {hash_type} hash, last changed: day {last_change}")
PYEOF
# Analyze login history
last -f /cases/case-2024-001/linux/logs/wtmp > /cases/case-2024-001/linux/analysis/login_history.txt
lastb -f /cases/case-2024-001/linux/logs/btmp > /cases/case-2024-001/linux/analysis/failed_logins.txt 2>/dev/null
# Check cron jobs for all users
echo "=== CRON JOBS ===" > /cases/case-2024-001/linux/persistence/cron_analysis.txt
# System cron
for cronfile in /mnt/evidence/etc/crontab /mnt/evidence/etc/cron.d/*; do
echo "--- $cronfile ---" >> /cases/case-2024-001/linux/persistence/cron_analysis.txt
cat "$cronfile" 2>/dev/null >> /cases/case-2024-001/linux/persistence/cron_analysis.txt
echo "" >> /cases/case-2024-001/linux/persistence/cron_analysis.txt
done
# User cron tabs
for cronfile in /mnt/evidence/var/spool/cron/crontabs/*; do
echo "--- User crontab: $(basename $cronfile) ---" >> /cases/case-2024-001/linux/persistence/cron_analysis.txt
cat "$cronfile" 2>/dev/null >> /cases/case-2024-001/linux/persistence/cron_analysis.txt
echo "" >> /cases/case-2024-001/linux/persistence/cron_analysis.txt
done
# Check systemd services for persistence
echo "=== SYSTEMD SERVICES ===" > /cases/case-2024-001/linux/persistence/systemd_analysis.txt
find /mnt/evidence/etc/systemd/system/ -name "*.service" -newer /mnt/evidence/etc/os-release \
>> /cases/case-2024-001/linux/persistence/systemd_analysis.txt
for svc in /mnt/evidence/etc/systemd/system/*.service; do
echo "--- $(basename $svc) ---" >> /cases/case-2024-001/linux/persistence/systemd_analysis.txt
cat "$svc" >> /cases/case-2024-001/linux/persistence/systemd_analysis.txt
echo "" >> /cases/case-2024-001/linux/persistence/systemd_analysis.txt
done
# Check authorized SSH keys (backdoor detection)
echo "=== SSH AUTHORIZED KEYS ===" > /cases/case-2024-001/linux/persistence/ssh_keys.txt
find /mnt/evidence/home/ /mnt/evidence/root/ -name "authorized_keys" -exec sh -c \
'echo "--- {} ---"; cat {}; echo ""' \; >> /cases/case-2024-001/linux/persistence/ssh_keys.txt
# Check rc.local and init scripts
cat /mnt/evidence/etc/rc.local 2>/dev/null > /cases/case-2024-001/linux/persistence/rc_local.txt
# Check /etc/profile.d/ for login-triggered scripts
ls -la /mnt/evidence/etc/profile.d/ > /cases/case-2024-001/linux/persistence/profile_scripts.txt
# Check for LD_PRELOAD hijacking
grep -r "LD_PRELOAD" /mnt/evidence/etc/ 2>/dev/null > /cases/case-2024-001/linux/persistence/ld_preload.txt
cat /mnt/evidence/etc/ld.so.preload 2>/dev/null >> /cases/case-2024-001/linux/persistence/ld_preload.txt
# Analyze bash history for each user
python3 << 'PYEOF'
import os, glob
print("=== SHELL HISTORY ANALYSIS ===\n")
suspicious_commands = [
'wget', 'curl', 'nc ', 'ncat', 'netcat', 'python -c', 'python3 -c',
'perl -e', 'base64', 'chmod 777', 'chmod +s', '/dev/tcp', '/dev/udp',
'nmap', 'masscan', 'hydra', 'john', 'hashcat', 'passwd', 'useradd',
'iptables -F', 'ufw disable', 'history -c', 'rm -rf /', 'dd if=',
'crontab', 'at ', 'systemctl enable', 'ssh-keygen', 'scp ', 'rsync',
'tar czf', 'zip -r', 'openssl enc', 'gpg --encrypt', 'shred',
'chattr', 'setfacl', 'awk', '/tmp/', '/dev/shm/'
]
for hist_file in glob.glob('/cases/case-2024-001/linux/users/*/.bash_history'):
username = hist_file.split('/')[-2]
print(f"User: {username}")
with open(hist_file, 'r', errors='ignore') as f:
lines = f.readlines()
print(f" Total commands: {len(lines)}")
flagged = []
for i, line in enumerate(lines):
line = line.strip()
for cmd in suspicious_commands:
if cmd in line.lower():
flagged.append((i+1, line))
break
if flagged:
print(f" Suspicious commands: {len(flagged)}")
for lineno, cmd in flagged:
print(f" Line {lineno}: {cmd[:120]}")
print()
PYEOF
# Check for known rootkit indicators
# Compare system binary hashes against known-good
find /mnt/evidence/usr/bin/ /mnt/evidence/usr/sbin/ /mnt/evidence/bin/ /mnt/evidence/sbin/ \
-type f -executable -exec sha256sum {} \; > /cases/case-2024-001/linux/analysis/binary_hashes.txt
# Check for SUID/SGID binaries (potential privilege escalation)
find /mnt/evidence/ -perm -4000 -type f 2>/dev/null > /cases/case-2024-001/linux/analysis/suid_files.txt
find /mnt/evidence/ -perm -2000 -type f 2>/dev/null > /cases/case-2024-001/linux/analysis/sgid_files.txt
# Check for suspicious files in /tmp and /dev/shm
find /mnt/evidence/tmp/ /mnt/evidence/dev/shm/ -type f 2>/dev/null \
-exec file {} \; > /cases/case-2024-001/linux/analysis/tmp_files.txt
# Check for hidden files and directories
find /mnt/evidence/ -name ".*" -not -path "*/\." -type f 2>/dev/null | \
head -100 > /cases/case-2024-001/linux/analysis/hidden_files.txt
# Check kernel modules
ls -la /mnt/evidence/lib/modules/$(ls /mnt/evidence/lib/modules/ | head -1)/extra/ 2>/dev/null \
> /cases/case-2024-001/linux/analysis/extra_modules.txt
# Check for modified PAM configuration (authentication backdoors)
diff /mnt/evidence/etc/pam.d/ /cases/baseline/pam.d/ 2>/dev/null \
> /cases/case-2024-001/linux/analysis/pam_changes.txt
| Concept | Description |
|---|---|
| /var/log/auth.log | Primary authentication log on Debian/Ubuntu systems |
| /var/log/secure | Primary authentication log on RHEL/CentOS systems |
| wtmp/btmp | Binary logs recording successful and failed login sessions |
| .bash_history | User command history file (can be cleared by attackers) |
| crontab | Scheduled task system commonly used for persistence |
| authorized_keys | SSH public keys granting passwordless access to an account |
| SUID bit | File permission allowing execution as the file owner (privilege escalation vector) |
| LD_PRELOAD | Environment variable that loads a shared library before all others (hooking technique) |
| Tool | Purpose |
|---|---|
| chkrootkit | Rootkit detection scanner for Linux systems |
| rkhunter | Rootkit Hunter - checks for rootkits, backdoors, and local exploits |
| AIDE | Advanced Intrusion Detection Environment - file integrity monitor |
| auditd | Linux audit framework for system call and file access monitoring |
| last/lastb | Parse wtmp/btmp for login and failed login history |
| Plaso/log2timeline | Super-timeline creation including Linux artifacts |
| osquery | SQL-based system querying for live forensic investigation |
| Velociraptor | Endpoint agent with Linux artifact collection capabilities |
Scenario 1: SSH Brute Force Followed by Compromise Analyze auth.log for failed SSH attempts followed by success, identify the attacking IP, check .bash_history for post-compromise commands, examine authorized_keys for added backdoor keys, check crontab for persistence, review network connections.
Scenario 2: Web Server Compromise via Application Vulnerability Examine web server access and error logs for exploitation attempts, check /tmp and /dev/shm for webshells, analyze the web server user's activity (www-data), check for privilege escalation via SUID binaries or kernel exploits, review outbound connections.
Scenario 3: Insider Threat on Database Server Analyze the suspect user's bash_history for database dump commands, check for large tar/zip files in home directory or /tmp, examine scp/rsync commands for data transfer, review cron jobs for automated exfiltration, check USB device logs.
Scenario 4: Crypto-Miner on Cloud Instance Check for high-CPU processes in /proc (live) or systemd service files, examine crontab entries for miner restart scripts, check /tmp for mining binaries, analyze network connections for mining pool communications, review authorized_keys for attacker access.
Linux Forensics Summary:
System: webserver01 (Ubuntu 22.04 LTS)
Hostname: webserver01.corp.local
Kernel: 5.15.0-91-generic
User Accounts:
Total: 25 (3 with UID 0 - 1 ANOMALOUS)
Interactive shells: 8 users
Recently created: admin2 (created 2024-01-15)
Authentication Events:
Successful SSH logins: 456
Failed SSH attempts: 12,345 (from 23 unique IPs)
Sudo executions: 89
Persistence Mechanisms Found:
Cron jobs: 3 suspicious (reverse shell, miner restart)
Systemd services: 1 unknown (update-checker.service)
SSH keys: 2 unauthorized keys in root authorized_keys
rc.local: Modified with download cradle
Suspicious Activity:
- bash_history contains wget to pastebin URL
- SUID binary /tmp/.hidden/escalate found
- /dev/shm/ contains compiled ELF binary
- LD_PRELOAD in /etc/ld.so.preload pointing to /lib/.hidden.so
Report: /cases/case-2024-001/linux/analysis/