brutal SSH attacks

[Vadym Chepkov]

On Feb 8, 2011, at 7:11 PM, Vadym Chepkov wrote:

> 
> On Feb 8, 2011, at 7:01 PM, Helmut Schneider wrote:
> 
>>>> Check your pflog. The ruleset itself seems fine (if it is complete and you did not forget to post
>>>> a vital part). We also can assume that pf is enabled, can we?
>>> 
>>> What should I be looking for in pflog? I can't find anything ssh related. I posted full ruleset too.
>> [...]
>>> [root at castor /var/log]# for log in pflog.?.bz2 ; do bzcat $log|tcpdump -r - port ssh ; done
>>> reading from file -, link-type PFLOG (OpenBSD pflog file)
>>> reading from file -, link-type PFLOG (OpenBSD pflog file)
>>> reading from file -, link-type PFLOG (OpenBSD pflog file)
>>> reading from file -, link-type PFLOG (OpenBSD pflog file)
>> 
>> Well...
>> 
>>> block drop in quick from <abusive_hosts> to any
>>> pass quick inet proto tcp from any to 38.X.X.X port = ssh flags S/SA keep state (source-track rule, max-src-conn 10, max-src-conn-rate 9/60, overload <abusive_hosts> flush global, src.track 60)
>> 
>> "block drop in quick log..." and "pass quick inet proto log" might be useful. BTW, what version of FreeBSD are you using? The machine isn't multi-homed, is it? 
> 
> 8.1-RELEASE-p1, just one external interface.
> 
> I will add "log" to "pass ssh", but what would I "block drop in quick" though?


Here are entries with pass in log enabled:

19:59:08.149358 rule 5/0(match): pass in on bce1: 93.174.31.134.36872 > 38.X.X.X.22: Flags [S], seq 441726758, win 5840, options [mss 1460,sackOK,TS val 395810874 ecr 0,nop,wscale 7], length 0
19:59:09.879718 rule 5/0(match): pass in on bce1: 93.174.31.134.37700 > 38.X.X.X.22: Flags [S], seq 442612509, win 5840, options [mss 1460,sackOK,TS val 395812607 ecr 0,nop,wscale 7], length 0
19:59:11.585464 rule 5/0(match): pass in on bce1: 93.174.31.134.38063 > 38.X.X.X.22: Flags [S], seq 452334454, win 5840, options [mss 1460,sackOK,TS val 395814310 ecr 0,nop,wscale 7], length 0
19:59:13.343901 rule 5/0(match): pass in on bce1: 93.174.31.134.38266 > 38.X.X.X.22: Flags [S], seq 460272696, win 5840, options [mss 1460,sackOK,TS val 395816072 ecr 0,nop,wscale 7], length 0
19:59:15.083747 rule 5/0(match): pass in on bce1: 93.174.31.134.39088 > 38.X.X.X.22: Flags [S], seq 451620226, win 5840, options [mss 1460,sackOK,TS val 395817812 ecr 0,nop,wscale 7], length 0
19:59:16.825914 rule 5/0(match): pass in on bce1: 93.174.31.134.39441 > 38.X.X.X.22: Flags [S], seq 449195625, win 5840, options [mss 1460,sackOK,TS val 395819550 ecr 0,nop,wscale 7], length 0
19:59:18.556231 rule 5/0(match): pass in on bce1: 93.174.31.134.39722 > 38.X.X.X.22: Flags [S], seq 452162408, win 5840, options [mss 1460,sackOK,TS val 395821284 ecr 0,nop,wscale 7], length 0
19:59:20.263343 rule 5/0(match): pass in on bce1: 93.174.31.134.40441 > 38.X.X.X.22: Flags [S], seq 466289680, win 5840, options [mss 1460,sackOK,TS val 395822987 ecr 0,nop,wscale 7], length 0
19:59:21.996759 rule 5/0(match): pass in on bce1: 93.174.31.134.40812 > 38.X.X.X.22: Flags [S], seq 466926642, win 5840, options [mss 1460,sackOK,TS val 395824721 ecr 0,nop,wscale 7], length 0
19:59:23.723164 rule 5/0(match): pass in on bce1: 93.174.31.134.41081 > 38.X.X.X.22: Flags [S], seq 470787551, win 5840, options [mss 1460,sackOK,TS val 395826451 ecr 0,nop,wscale 7], length 0
19:59:25.424186 rule 5/0(match): pass in on bce1: 93.174.31.134.41808 > 38.X.X.X.22: Flags [S], seq 456764787, win 5840, options [mss 1460,sackOK,TS val 395828152 ecr 0,nop,wscale 7], length 0


No idea, why it didn't stop after 9 attempts.

Vadym