[SR-Users] dictionary attacks

[Daniel-Constantin Mierla]

I watched live an attack on voipuser.org while running 3.1 before 
release. It lasted 18 hours. I didn't want to ban it because was useful 
for testing and see if it reveals any weak. In most of the cases it hit 
pike module. I got some data and plan to make an article about it soon.

Anyhow, as a result of that, default config for kamailio has a section 
for detecting and banning such "bad" IPs, using pike to detect floods 
and htable to keep it blocked. Search WITH_ANTIFLOOD directive. It can 
be enhanced like you pointed here, so if the authorize fails, add the IP 
in the banned list stored in htable.

Using fail2ban together with IP tables has the advantage of dropping the 
packets before getting to application and eating cpu, although in the 
case of voipuser.org the cpu was not affected much - the rate was 
170-200 requests per second.

Cheers,
Daniel


On 10/24/10 3:06 PM, Sergey Okhapkin wrote:
> I'm second for fail2ban. I block IP addresses with failed registration
> attempts for 1 hour. Here is my setup:
>
> kamailio.cfg:
>
> if (is_method("REGISTER")) {
>          if(www_authorize("", "subscriber")<  0) {
>                if($rc == -1) {
>                       xlog("L_INFO","Invalid username from $proto:$si:$sp\n");
>                       sl_send_reply("200","OK");
>                 } else
>                       www_challenge("", "0");
>                 exit;
>           }
> ....
>
> /etc/fail2ban/filter.d/openser.conf:
>
> [Definition]
> #_daemon = kamailio
> failregex = Invalid username from ...:<HOST>:
>
> /etc/fail2ban/jail.conf:
>
> findtime  = 600
>
> [openser-iptables]
> enabled  = true
> filter   = openser
> action   = iptables-allports[name=OPENSER, protocol=all]
> logpath  = /var/log/openser/openser # Replace with your sr log location
> maxretry = 10
> bantime = 3600
>
>
> On Sunday 24 October 2010, Uriel Rozenbaum wrote:
>> Juha,
>>
>> I think we should be specially careful about black-lists. We receive
>> many of these attacks in a per-day basis and a lot of them are from
>> residential addresses or university, so I'm guessing some kind of worm
>> or trojan performing the attack from various IPs.
>>
>> If you have the time, try fail2ban deamon. It can relate some
>> brute-force events and act accordingly blocking an IP on iptables,
>> executing a script. You send to "jail" those addresses for a period of
>> time, then you can get them out again; and of course you can manually
>> revert.
>>
>> Last, as a description of the attacks I saw, first it runs an NMAP
>> like scan checking which IPs answer from 5060, then it starts sending
>> registers (usually asterisk answers 404 if the user does not exist),
>> then when the proxy challenges, it interprets the user is found and
>> starts making dictionary attacks on the password (1234, admin, and so
>> on). Keep safe complicated passwords, make kamailio challenge
>> everything and you'll be safe. and again, fail2ban is a pretty good
>> solution for brute force.
>>
>> This might help you finding a solution for your attacks.
>>
>> Cheers,
>> Uriel
>>
>> On Sun, Oct 24, 2010 at 8:54 AM, Juha Heinanen<jh at tutpro.com>  wrote:
>>> while doing some tests, i noticed that one of my proxies started to
>>> receive lots of register requests with different user names starting
>>> from a letter.  there was also invite attempts in the logs.  they came
>>> from ip 202.82.16.99 which according to traceroute is somewhere in
>>> china.
>>>
>>> should we start publishing a black list of these attack ip addresses?
>>>
>>> -- juha
>>>
>>> _______________________________________________
>>> SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing list
>>> sr-users at lists.sip-router.org
>>> http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users
>> _______________________________________________
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>> sr-users at lists.sip-router.org
>> http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users
>>
>
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-- 
Daniel-Constantin Mierla
http://www.asipto.com