[asterisk-users] Checking blank CallerID in Dialplan

[Fred Posner]

On May 20, 2010, at 12:43 PM, Myles Wakeham wrote:

> I am trying to implement a change to our Dialplan that will thwart 
> tele-spammers that are calling us with blanked out caller ID.
> 
> The caller IDs seem to vary between originating callers when they block 
> caller ID.  I've seen the following:
> 
> "anonymous"
> ""
> 
> So I'm checking for these.  However recently one company seems to be 
> bypassing this, so what I wanted to do was implement some logic that 
> checks for actual numbers in the caller ID.
> 
> We have a couple of different SIP providers for incoming calls.  Some 
> prefix numbers with a +  and others don't.  But I'm logging incoming 
> calls that are getting through our tele-spam filter and it seems that 
> they are blank, but I suspect they contain empty spaces which is why our 
> matches don't work.
> 
> Does anyone have some sample DialPlan code that they are using to thwart 
> incoming calls with no caller ID?  I was thinking of maybe converting 
> the caller ID num to a numeric value and testing for 'not equal to 0' 
> but that won't work with the + prefix.
> 
> All suggestions greatly appreciated.
> 
> Myles

In my opinion this is one of the greatest aspects of Asterisk... it's ability to do custom things just as this. Much like anything IT, there are many ways of approaching this. Different people have different solutions.

One can be an API lookup to something such as whocalled.us (which has an AGI for asterisk).

Another can be a localized black list.

An yet another can be a localized white list. (If the number doesn't match a known, "approved" number, then give it some sort of IVR or screening)

I don't get hit that much anymore, so I'm still with the modified blacklist approach. Unknown callers (0000000000, 0123., Anonymous, Unknown, etc.) get screened and known telemarketers go to the torture I talked about at http://bit.ly/bbhho

---fred
http://qxork.com