GEN:SID 1:601
Message RSERVICES rlogin LinuxNIS
Summary This event is generated when an attempt is made to exploit a
machine using Network Information Services (NIS).
Impact Unknown. This is traffic that should not be seen when using NIS and
remote login services.
Detailed Information This event is generated when spurious data is sent to the rlogin service
running on a machine that is using NIS.
Affected Systems  
Attack Scenarios An attacker needs to generate this traffic and send it directly to a
machine. This is not normal network behavior.
Ease of Attack Simple, no exploit software required
Corrective Action Investigate logs on the target host for further details and more signs of suspicious activity

Use ssh for remote access instead of rlogin.
Additional References