SMTP brute force attack?

[Seth Milder <mrseth () PHYSICS GMU EDU>]

I keep getting this in my logs. Is someone trying to find a valid
username so they can crack my box? Or maybe this is a spammer trying to
find a way to get my machine to relay their crap? Any advice is
definitely welcome.


Thanks,

Seth



Nov 23 21:01:09 ns sendmail[21886]: NOQUEUE: Null connection from [x.x.x.x]
Nov 23 21:01:18 ns sendmail[21888]: VAA21888: <haha () victimhost com>...
User unknown
Nov 23 21:17:45 ns sendmail[21912]: VAA21912:
<F10981N9776 () victimhost com>... User unknown
Nov 23 21:17:46 ns sendmail[21913]: VAA21913:
<F10981N9776 () victimhost com>... User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <robert () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <mark () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <chris () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <greg () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915:
<michael () victimhost com>... User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <peter () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <joe () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <gary () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <bill () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <frank () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <brian () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <dan () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <steve () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <eric () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <jeff () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <scott () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <david () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <bob () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <rick () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <paul () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <dave () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <mike () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <ken () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <jason () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <kevin () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <john () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <rob () victimhost com>...
User unknown
Nov 23 21:17:49 ns sendmail[21915]: VAA21915: <tom () victimhost com>...
User unknown
Nov 23 21:19:13 ns sendmail[21919]: VAA21919:
<alt-chinese-text () victimhost com>... User unknown
Nov 23 21:24:23 ns sendmail[21935]: VAA21935:
<chinese-talk-misc () victimhost com>... User unknown
Nov 23 23:31:06 ns sendmail[22186]: NOQUEUE: Null connection from [x.x.x.x]
Nov 23 23:31:14 ns sendmail[22188]: XAA22188: <haha () victimhost com>...
User unknown