I doubt the attackers even went through the hustle to gain root (no need, anyone can start stuff on (unfiltered) 8080).
Finding a vulnerable .php/cgi for executing commands on the Server under the uid of the Webserver sounds much easier to me.
1. Scan for vulnerable Servers
2. upload trojansite.tgz
3. unpack to some world-writable/executable directory like for e.g. /tmp/.../
4. fire up nginx serving the trojans
5. Profit (5 ?! omg, people really have to work for their monies these days)