[OpenSIPS-Users] Fraud_detection module

[Liviu Chircu]

Hi, Denis!

First of all, thank you for taking the time to gather this nice data! 
Looking at the calls, to me it looks like the module behaved as 
expected. Here are some thoughts:

- all call durations were less under 1500 seconds, while your fraud rule 
is set to 3600 seconds, so it never got triggered.

- the "calls-per-minute" rule worked! Your rule was set to max 6 cpm, 
thus calls #7 - #9 to prefix "810" were considered fraudulent (at 
01:41), as the caller was starting to exceed this quota. The proper 
critical warnings were raised, calls blocked, emails sent.

- the attacker now _learned_ about your 6 cpm limitation and _lowered_ 
his cpm to 3 during the following 10 hours (until 11:08), thus bypassing 
the cpm rate limiting, managing to place 21 fraudulent calls.

It seems like the 21 successful fraudulent calls between 03:06 - 11:08 
could _maybe_ have been avoided by setting a better value for 
"sequential-calls". This is a bit tricky though, as we also don't want 
to block calls of honest users because of false positives.

Regards,

Liviu Chircu
OpenSIPS Developer
http://www.opensips-solutions.com

On 11.11.2016 09:38, Denis wrote:
> Re: [OpenSIPS-Users] Fraud_detection module Hello, Liviu!
>
> OK, thank you.
>
> Additionally i will ask you to analyze one case.
> In attachment you can find a log of calls, which were made by one user 
> some time ago (with the number 1234567). It`s a fraud.
> Also i attached a piece of opensips.cfg related to a fraud detection 
> (see script.txt). When critical event triggered Opensips sends email 
> to some address (see script.txt).
>
> As you can see in the call log, fraud began at 01:40 2016-10-01. Value 
> of the field "sip_reason" "fraud_detected" means that fraud_module 
> detects the fraud and a call was discarded by script logging (see 
> script.txt)
> First email about that i received at 01:41 with fraud param " calls 
> per minute".
> Next email i received only at 11:08 with fraud param "total calls".
>
> Between these two time stamps i have no emails about fraud, and as you 
> can see from the call log, there were many successful calls in this 
> period with "big" duration.
>
> Fraud_detection table had such content:
> profileid = 1
> prefix = 810
> start_hour = 00:00
> end_hour = 23:59
> daysoftheweek = Mon-Sun
> cpm_critical = 6
> call_duration_critical = 3600
> tatal_calls_critical = 30
> concurant_calls_critical = 30
> sequential_calls_critical = 5000
>
> The questions is:
> - Why module didn`t detect fraud based on "call duration"?
>
> Thank you.
>
> mailto:denis7979 at mail.ru
>
>
> 	Upon looking through the source code, it seems that calls_per_min / 
> total_calls / concurrent_calls are also reset to 0 every time a new 
> rule is matched, or if the day has changed since we last matched the 
> current rule.
> I will make sure this info ^ is more easily accessible: either in a 
> new tutorial section or the module doc.
> Regards,
> Liviu Chircu
> OpenSIPS Developer
> http://www.opensips-solutions.com
> On 10.11.2016 16:29, Denis wrote:
>
> 	Re: [OpenSIPS-Users] Fraud_detection module
>
> 	Hello, Liviu!
>
> Thank you for your answer.
>
> About 2)
>
> "Calls per minute" - ok, but what about other parameters?
> For example, "total calls"?
> Suppose we have 09:00 - 17:00, Mon-Fri, and "total calls" = 30.
> If in Mon user makes 25 calls, on Tue since 09:00 counts of  "total 
> calls" begin from 0 or 25?
>
> mailto:denis7979 at mail.ru <mailto:d.putyato at ptl.ru>
>
>
> 	Hi, Deniz!
> Answers below.
> Regards,
> Liviu Chircu
> OpenSIPS Developer
> http://www.opensips-solutions.com
> On 10.11.2016 15:18, Denis wrote:
>
> 	Re: Fraud_detection modul
>
> 	Hello!
>
> Opensips 2.2.1
>
> A couple of questions about fraud_detection:
>
> 1) In documentation says "*consecutive calls* to the same destination 
> ". Same destination = same number, or prefix?
>
> Same prefix, taken from the fraud detection rule
>
> 	
> 2) At the beginning of the next period, a counts of events begin 0?
>
> The module uses a gliding window of 60 seconds, in order to keep track 
> of "calls per minute". When changing time intervals, hence putting new 
> thresholds in place, the "calls per minute" will not reset. In other 
> words, when switching intervals, the new "calls per minute" thresholds 
> will initially work with calls placed during the last minute when the 
> old thresholds were in place.
>
> 	
> 3) is there any method to reset counts of events for certain user?
>
> Currently there is no way of doing this.
>
>
> 	
> 4)  what is the value used to calculate duration in fraud_module, 
> minutes or seconds?
>
> It should be "seconds", I will fix the misleading example in the 
> tutorial.
>
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