The vsftpd 2.3.4 backdoor (CVE-2011-2523) is a famous example of a software supply chain attack. Between June 30 and July 3, 2011, a malicious version of the "Very Secure FTP Daemon" source code was uploaded to the official distribution site. This compromised version contained a hidden trigger: if a user logged in with a username ending in a smiley face (:)), the server would spawn a root shell listening on TCP port 6200. Technical Breakdown of the Exploit
The exploit is available on GitHub, and installing it is relatively straightforward. Here are the steps: vsftpd 208 exploit github install
Network Monitoring: Employing Intrusion Detection Systems (IDS) or firewalls can help identify and block unusual traffic, such as unauthorized attempts to connect to port 6200. The vsftpd 2
/* ... inside string handling functions ... */
if (p_str->len == 2 && p_str->p_buf[0] == ':' && p_str->p_buf[1] == ')')
// Backdoor logic trigger