Filtering VOIP Calls

[TigerCustom]

Hi all,

I have a client who is reporting a massive amount of incoming spam/unwanted VOIP calls, being displayed as such in the caller ID according to them. Is there a smart way of filtering out any VOIP calls that tend to be spam, i.e., that don't go through a wire/carrier at some point? Thanks!

 

[cobaltit]

https://www.3cx.com/community/threads/information-to-provide-when-requesting-help.67558/

Not really much information provided by my first thought would be that you are using STUN. Using a SBC (3CX or otherwise) would resolve this.

 

[leejor]

If you are talking about Direct SIP calls to the set, some make of sets, have an option to disregard any calls not from the server. What sets are you using? I'm assuming these calls do not pass through 3CX.

 

[TigerCustom]

Hi all,

Just an update here - I apologize as I'm not nearly as knowledgeable on this system as I would like. We have the numbers PTSN-managed by Flowroute. The 3CX client is strictly cloud-based and the end-user is using a soft phone, no IP phones, no SBC on-site. The entire setup is very bare-bones and they're using just one extension at the moment. Any further details that I could provide that would be useful, please let me know where I can source that from and any further advice moving forward on this issue would be greatly appreciated.

Thank you!

 

[leejor]

If the calls come in over the Flowroute trunks, then they will show in the 3CX Activity Log. The best thing is to confirm that that is happening, otherwise everything is speculation.

 

[TigerCustom]

leejor, I did run a quick report and had the receptionist review and mark what numbers were spam.. looks like it was a big mixture, largely local, along with some out of state and toll free sprinkled in. Numbers such as 4252438256, 4256893302, 4256893280, 2068769861, 18666136855, 2532302434, 9493315457. I'm not sure where to go from here since they just seem to be coming from all sorts of angles. Any advice would be greatly appreciated.

 

[leejor]

But, does the 3CX Activity Log show that the calls are coming in over your SIP trunks, or might they be direct SIP calls to the extension?

If they come in over your trunks, then see if your provider can assist at all in bocking the calls. That may not be possible if they do not originate from one source (coming in to them), and the caller ID appears legitimate. If your provider discovers that the majority of spam calls come to them from one specific provider, they may be able to put pressure on them, to attempt to block the calls. This involves some work, so I wouldn't hold my breath.

Spam callers will usually change their caller Id so that it cannot be blocked, in many cases they will also make it look to be a local number calling you in the hopes you will answer.

One sure fire method to stop Spam calls is to require the caller to enter a number in an IVR. Automated SPAM calls cannot do this (yet). Set up an IVR for your main number. Keep the message short and "informational"..."Thank you for calling ABC Widgets, our hours are 8 am to 5 pm Monday through Friday, street-side pick-up is available at our Oak street location, please press 1to be connected our receptionist.

You've given them some information that they may not be aware of, and stopped SPAM calls at the same time.

 

[TigerCustom]

Thanks for that. This is the interesting thing - there seems to be a lot of variation in how these calls are coming through.. most through the main line ring group, some others directly to extension, and others in various other odd protocols. I'm attaching a capture of the log with the calls that were marked as spam to show in better detail.



Curious what your thoughts are on all of that.

But also good call on the IVR - that is a surefire way to at least deflect spammers en masse. If we can't get to the bottom of this otherwise, I'll certainly push for that as a solution. Thank you!

 

[leejor]

I have to assume that many "groups" placing SPAM calls simply dial numbers in sequence, so if you receive a call on 5551211, you will probably soon get a call on 5551212, if you have several numbers in the same "block".

I've seen that happen many times on numbers at work, 4 of which are in sequence. But, who knows, they could be using any sort of sequence dialling, even random, I just assume that they keep track of whether there was an answer, or not. There are no doubt several going at the same time, so it's going to be hard to keep track, especial when they constantly change caller ID.

One can only hope that new measures now being implemented by providers will eventually decrease the number of calls, but, short of shutting these callers down at the source, I am not confident that they will be eliminated completely, as long as there is money to be made placing them.