JENKINS-44166 of the Jenkins P4 plugin modified the plugin to work in cases when a pre-login perforce triggers was being used.
The 'fix' for the above issue:
now means that a 'p4 login -s' call is made to the Perforce server during each and every call to the isLogin() method. This can literally result in 10,000's of 'p4 login -s' requests an hour and cause the server to lock up (by using up all the available TCP sockets).
The consequence being very similar to a DoS attach on the Perforce server.