Talos has been monitoring a persistent threat for quite some time, a group they refer to as SSHPsychos or Group 93. This group is well known for creating significant amounts of scanning traffic across the Internet while, its primary focus has been SSH brute force attacks. Based on passive DNS data the first activity was seen in June 2014.
Talos is a Security Intelligence and Research Group made up of leading threat researchers supported by sophisticated systems to create threat intelligence for Cisco products that detects, analyses and protects against both known and emerging threats.
Read the full analyses here - https://blogs.cisco.com/security/talos/sshpsychos