Malware
SALTWATER
According to Mandiant, SALTWATER is a module for the Barracuda SMTP daemon (bsmtpd) that has backdoor functionality.
SALTWATER is a Linux malware family.
Background
Mandiant identifies SALTWATER as a backdoor-capable module for the Barracuda SMTP daemon (bsmtpd). It can transfer arbitrary files in either direction, run commands, and act as a proxy and tunnel. The backdoor works by hooking the send, recv, and close syscalls through the third-party kubo/funchook library, and is composed of five components that the binary largely labels as "Channels." Beyond their backdoor and proxying roles, these components display the usual backdoor behaviors.
Source: Malpedia (Fraunhofer FKIE).