Interesting log file

[Burke, Thomas G.]

Hey all,
 
    I have *NEVER* seen this before - any idea what it means?
 
    -Tom
 

Security Violations 
=-=-=-=-=-=-=-=-=-= 
Jun 10 14:33:20 tomii-gate login: FAILED LOGIN 1 FROM (null) FOR                       , User not known to the underlying authentication module

Jun 10 14:33:21 tomii-gate login: FAILED LOGIN 2 FROM (null) FOR , User not known to the underlying authentication module

Jun 10 14:33:22 tomii-gate login: FAILED LOGIN 3 FROM (null) FOR , User not known to the underlying authentication module

Jun 10 14:33:35 tomii-gate login: FAILED LOGIN SESSION FROM (null) FOR  , User not known to the underlying authentication module