The recent Log4j vulnerability (CVE-2021-44228) has caused widespread concern, but it's crucial to understand that Apache HTTP Server (Apache2) itself does not use Log4j for logging. The server relies on its own logging mechanism (mod_log_config), making it inherently unaffected by this specific vulnerability.

The log entries you're observing with patterns like ${jndi:ldap://} are actually scan attempts from automated bots probing for vulnerable systems. These include:

• Kryptos Logic's scanning infrastructure (research/honeypot)
• Malicious actors testing for Log4j exposure
• DNS callback attempts (like dnslog.cn domains)

While Apache2 isn't vulnerable, you should:

1. Verify Java Applications: Check if you're running any Java-based applications (Tomcat, Solr, etc.) that might use Log4j:

   # Search for log4j files in common locations
   find / -name "log4j*.jar" -type f 2>/dev/null
   

2. Monitor for Suspicious Files:

   # Check for recently created .class files
   find / -name "*.class" -mtime -7 2>/dev/null
   

3. Implement Web Application Firewall Rules to block Log4j exploit patterns:

   # Example ModSecurity rule
   SecRule ARGS|ARGS_NAMES|REQUEST_HEADERS|REQUEST_BODY "@rx \$\{jndi:(ldap|rmi|dns):" \
       "id:1000,phase:2,deny,status:403,msg:'Potential Log4j Exploit Attempt'"
   

For defense-in-depth:

• Network Segmentation: Isolate internet-facing servers
• Outbound Filtering: Block suspicious DNS lookups
• Log Monitoring: Set up alerts for JNDI patterns

Here's a Python script to scan Apache logs for exploit attempts:

import re
from collections import defaultdict

def scan_log_for_jndi(log_file):
    pattern = re.compile(r'\$\{jndi:(ldap|rmi|dns):[^\}]+}')
    hits = defaultdict(int)
    
    with open(log_file) as f:
        for line in f:
            matches = pattern.findall(line)
            if matches:
                ip = line.split()[0]
                hits[ip] += 1
                
    return dict(hits)

if __name__ == "__main__":
    results = scan_log_for_jndi('/var/log/apache2/access.log')
    for ip, count in results.items():
        print(f"Potential attacker: {ip} (attempts: {count})")

• Apache2 itself is safe - no need to panic
• Focus on Java applications running alongside Apache
• Maintain good security hygiene (patches, monitoring)
• Consider implementing the detection mechanisms shown above

Your Apache 2.4.38 logs show clear attempts to exploit the Log4j vulnerability (CVE-2021-44228). The patterns like ${jndi:ldap://[malicious-domain]} are telltale signs of scanning attempts. These entries come from:

• Kryptos Logic (legitimate security researchers scanning for vulnerable systems)
• dataastatistics.com (likely malicious actors)
• dnslog.cn (common domain for vulnerability verification)

Apache HTTP Server (apache2) does not use Log4j for its core logging functionality. It uses its own logging mechanism (mod_log_config). The vulnerability attempts you're seeing are:

1. Automated internet-wide scanning
2. Attempts to exploit any potentially vulnerable Java-based applications behind your web server

For your specific case (Apache on Raspberry Pi OS):

# 1. Verify no Java applications are running behind Apache:
ps aux | grep java

# 2. Check for unexpected .class files (though unlikely on pure Apache):
find / -name "*.class" -type f -mtime -7

Since you're running a standard Apache installation without Java components, you can:

• Monitor logs for repeated attempts
• Consider blocking scanner IPs if they become intrusive

For defense-in-depth, even on non-vulnerable systems:

# Add these to your Apache configuration:
<IfModule mod_headers.c>
    Header always unset User-Agent
    Header always unset Referer
    RequestHeader unset User-Agent
    RequestHeader unset Referer
</IfModule>

Create a monitoring script to detect exploitation attempts:

#!/bin/bash
# log4j_scan_detect.sh
LOGFILE="/var/log/apache2/access.log"
PATTERN='\$\{jndi:(ldap▼显示?|rmi|dns):\/\/'

tail -n0 -F "$LOGFILE" | while read LINE; do
    if [[ "$LINE" =~ $PATTERN ]]; then
        echo "[WARNING] Potential Log4j exploit attempt detected:"
        echo "$LINE"
        # Optional: Add blocking rule
        IP=$(echo "$LINE" | awk '{print $1}')
        iptables -A INPUT -s "$IP" -j DROP
    fi
done

To be absolutely certain your system isn't affected:

# Check for any Java applications that might use Log4j:
dpkg -l | grep -E 'log4j|java|jre|jdk'

# Verify Apache modules:
apache2ctl -M | grep -i log

Remember that while Apache HTTP Server itself isn't vulnerable, any Java applications you might be running behind it (like Tomcat) could be at risk.