title: Understanding rkhunter warnings
body: <p>I got paranoid and ran both chkrootkit and rkhunter to scan for rootkits.  Doesn't look like chkrootkit found anything, but rkhunter returned some warnings.  I think many might be false positives, but I'm mostly worried about the 'possible rootkit strings' and the three suspect files.  Any explanations would be greatly appreciated!! Thank you!</p>
  
  <pre><code>Performing file properties checks
  /usr/bin/fuser                                           [ Warning ]
  /usr/bin/whatis                                          [ Warning ]
  /usr/bin/shasum                                          [ Warning ]
  
  Performing additional rootkit checks
  Checking for possible rootkit strings                    [ Warning ]
  
  Performing checks on the network interfaces
  Checking for promiscuous interfaces                      [ Warning ]
  
  Performing system boot checks
  Checking for system startup files                        [ Warning ]
  
  Performing system configuration file checks
  Checking if SSH root access is allowed                   [ Warning ]
  Checking if SSH protocol v1 is allowed                   [ Warning ]
  
  Performing filesystem checks
  Checking for hidden files and directories                [ Warning ]
  </code></pre>
  
  <p>Warnings in the log file:</p>
  
  <pre><code>[17:00:44] Info: No mail-on-warning address configured
  [17:01:25]   /usr/bin/fuser                                  [ Warning ]
  [17:01:25] Warning: The command '/usr/bin/fuser' has been replaced by a script: /usr/bin/fuser: a /usr/bin/perl -w script text executable, ASCII text
  [17:01:36]   /usr/bin/whatis                                 [ Warning ]
  [17:01:36] Warning: The command '/usr/bin/whatis' has been replaced by a script: /usr/bin/whatis: POSIX shell script text executable, ASCII text
  [17:01:37]   /usr/bin/shasum                                 [ Warning ]
  [17:01:37] Warning: The command '/usr/bin/shasum' has been replaced by a script: /usr/bin/shasum: a /usr/bin/perl script text executable, ASCII text
  [17:03:28] Warning: Checking for possible rootkit strings    [ Warning ]
  [17:04:07]   Checking for promiscuous interfaces             [ Warning ]
  [17:04:07] Warning: Possible promiscuous interfaces:
  [17:04:09]   Checking for system startup files               [ Warning ]
  [17:04:09] Warning: No system startup files found.
  [17:04:10]   Checking if SSH root access is allowed          [ Warning ]
  [17:04:10] Warning: The SSH configuration option 'PermitRootLogin' has not been set.
  [17:04:10]   Checking if SSH protocol v1 is allowed          [ Warning ]
  [17:04:10] Warning: The SSH configuration option 'Protocol' has not been set.
  [17:04:17]   Checking for hidden files and directories       [ Warning ]
  [17:04:17] Warning: Hidden file found: /usr/share/man/man5/.rhosts.5: troff or preprocessor input text, ASCII text
  </code></pre>