TELECOM Digest OnLine - Sorted: Re: VoIP

Re: VoIP

T. Sean Weintz (
Fri, 29 Apr 2005 10:24:52 -0400

Choreboy wrote:

> For several months I've been getting calls with spoofed Caller IDs. I
> understand spoofing requires either VoIP or a PBX system with DSL.

> Can anybody with cable internet access and suitable software make VoIP
> calls?

> The other day I received a wrong-number call from an exchange belonging
> to Level 3 Communications. Among other services, they offer residential
> VoIP services through wholesalers such as ISPs and cable operators. I'm
> confused. Does a consumer need these services to use VoIP?

> [TELECOM Digest Editor's Note: I don't think either 'VOIP' or 'PBX system'
> have anything to do with it. If I understand correctly what I have
> read here in the Digest, it requires a 'PRI' type thing; that is, a
> multi-channel set of lines going to DID, or Direct Inward Dialing,
> which would, I guess, be similar to a PBX arrangement. Companies who
> have those lines _can_ set the caller ID to be whatever is appropriate
> in their instance. I suspect the fact that the ID shown was that
> company may have been just coincidental. You do need either cable
> internet or DSL to use VOIP; regular 'dialup' lines are just not wide
> enough or fast enough to do VOIP. But other than having DSL or cable,
> VOIP takes nothing especially fancy; just an adapter box from the
> place where you get the VOIP service and any regular telephone
> instrument will do the job. And if you planned on totally getting
> rid of your landline phone taking VOIP instead, that is generally
> not possible with DSL, since most telcos will not give stand-alone

Caller ID CAN be spoofed using VOIP. Apperently SIP allows for this, and
some VOIP providers leave this feature open for customers to use/abuse.
I know hackers were spoofing caller ID over VOIP using the ASTERISK open
source PBX system which lets you set all the nitty gritty SIP parameters
-- apparently including the CLID string. From what I understand, some
providers filter this at their switch, some don't ...

PRI's are a standard type of high cap ISDN line (as opposed to BRI,
the low cap vesrion). I think caller ID can be spoofed from EITHER
type of ISDN line, assuming one has the right type of equipment
plugged into it (which usually means a PBX switch)

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