From the intelligence gathering phase, we can see that there are numerous services running on the target. Hosts information also reveals that the target operating system is Linux-based. Let us search for one of the vulnerabilities within Metasploit and try to find the matching exploit module:

We can see that we already have a module in Metasploit that targets the vulnerable service found. After exploring the details at http://www.securityfocus.com/bid/48539/discuss and http://scarybeastsecurity.blogspot.in/2011/07/alert-vsftpd-download-backdoored.html, we can easily figure out that the vulnerability was intentionally put into the software and was carrying a backdoor that can be triggered remotely on the vulnerable system.