Identifying suspicious remote hacking activity on a Linux server requires vigilance and the ability to recognize various indicators. Here's a list of indicators to consider along with commands or tools to investigate them:
Unusual Network Traffic:
Monitor network traffic for unusual patterns or unexpected connections.
sudo tcpdump -i eth0 -n -nn
sudo netstat -tuln
Failed Login Attempts:
Check for repeated failed login attempts, especially for privileged accounts.
sudo tail -n 100 /var/log/auth.log
sudo grep "Failed password" /var/log/auth.log
Unexpected Processes:
Look for unfamiliar or suspicious processes running on the server.
sudo ps aux
sudo top
Check Process Tree:
Examine the process tree to see parent-child relationships.
pstree
Monitor Process Creation:
Watch for new processes being created in real-time.
watch 'ps aux'
Identify Parent Processes:
Look for unusual parent processes spawning new ones.
ps -eo pid,ppid,cmd --sort=-%cpu | head
Check Process Start Times:
Review the start times of processes for anomalies.
ps -eo pid,ppid,cmd,lstart --sort=start_time
Investigate Suspicious Processes:
Examine suspicious processes in detail.
sudo lsof -p <PID>
Monitor System Logs:
Review system logs for process-related events.
tail -n 100 /var/log/syslog
tail -n 100 /var/log/auth.log
Look for Process Listening on Network Ports:
Check for processes listening on unusual network ports.
sudo netstat -tulnp
Analyze Process Executable Paths:
Examine the paths of process executables for irregularities.
sudo ls -l /proc/<PID>/exe
Check Process Environment Variables:
Review environment variables of suspicious processes.
sudo cat /proc/<PID>/environ
Inspect Open Files and Network Connections:
Investigate open files and network connections of suspicious processes.
sudo lsof -p <PID>
sudo netstat -atunp | grep <PID>
Rootkit Detection:
Scan for rootkits to detect any unauthorized modifications.
sudo rkhunter --check
sudo chkrootkit
Unusual File Changes:
Monitor for unauthorized modifications to critical system files.
sudo find / -mtime -1 -type f
sudo tripwire --check
sudo aide --check
Anomalies in System Logs:
Review system logs for any unusual or unexpected entries.
sudo tail -n 100 /var/log/syslog
Spike in Resource Usage:
Look for sudden increases in CPU, memory, or disk usage.
sudo top
sudo iotop
Unauthorized Access:
Check for unauthorized login sessions or access attempts.
sudo last
sudo w
Unexplained Changes in User Accounts:
Review changes to user accounts, especially new or modified accounts.
sudo cat /etc/passwd
sudo cat /etc/shadow
Abnormal Outbound Connections:
Investigate unexpected outbound connections from the server.
sudo netstat -tuln
Rootkit Detection:
Scan for rootkits or unauthorized system modifications.
sudo rkhunter --check
sudo chkrootkit
Security Alerts from IDS/IPS:
Monitor alerts from Intrusion Detection Systems (IDS) or Intrusion Prevention Systems (IPS).
sudo service snort status
sudo service suricata status
Unexpected Privilege Escalation:
Check for any unexpected changes in user privileges or roles.
sudo grep -i 'sudo' /var/log/auth.log
Regularly monitoring these indicators can help identify suspicious remote hacking activity on your Linux server. It's crucial to establish proactive security measures and respond promptly to any detected anomalies to mitigate potential risks.
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