The el.PHP web shell is a PHP-based mailing script used for crafting and delivering spam emails. The script has been observed in exploitation campaigns whereby the attacker is utilizing vulnerable hosts for mass email spam. The script is designed to send phishing emails masquerading as legitimate PayPal service emails. Additionally, a perl-based IRC bot was also obtained from the malicious C2 server observed in the same campaign. Once executed, the perlbot connects back to an attacker-owned IRC server and awaits further commands.
- A remote attacker uploads a PHP-based mailing script and a perl IRC bot to the compromised host. The attacker executes the script forcing the vulnerable host to send unsolicited spam emails and join IRC botnet.
The attacker must be able to send crafted packets to the target system.
Alert Logic Coverage
Alert Logic® has evaluated its customer base for exposure to the exploit and has developed signatures for mitigating the threat depending on the security service in place.
The Network-Based Intrusion Detection System (IDS) has been updated with the new signatures for this exploit when detected via Alert Logic Threat Manager™. If this signature is detected, an incident is generated in the Alert Logic console.
Recommendations for Mitigation
The attacker must have exploited some other entry vector to gain access to the local victim host. Ensure that all software on internet-facing hosts is up-to-date.