Best to Avoid Doing IP PBX Style VoIP via BT’s Home Hub Routers

Customers of BT’s consumer broadband service should avoid using the ISPs Home Hub routers for business style VoIP phone setups because of a seemingly deliberate built-in weakness that, no matter what security settings you choose on the hub, it will always leave port 5060 open.

Admittedly we can’t think why anybody would want to use a consumer grade router like the HomeHub for operating an IP PBX style Voice-over-IP system, except perhaps as part of a techy experiment. Generally you’re better off getting a proper piece of business focused kit.

But never the less it appears as if a number of businesses have fallen foul of this security flaw (some of which were sent BT’s consumer Home Hub instead of the needed Business Hub) and in so doing have left themselves exposed to hackers who can break into connected VoIP systems.

The sorry tale is covered in much detail over at The Register, which reveals that no matter what you do (e.g. blocking all incoming ports, setting UPnP off, using 256bit passwords etc.) the standard port for VoIP (5060) will always remain open to any incoming connections and the hub will even do the NAT for you until it can find a working SIP device.

On the one hand this makes life easier for those trying to setup the BT VoIP service, while on the other it also makes it easier for hackers to smuggle attack traffic through the Hub in order to break into SIP accounts via brute-force.

BT’s Statement

BT has investigated similar issues and concluded that there is no fault with the way BT’s Consumer Home Hubs operate to allow VoIP calls over the internet.

It’s inappropriate to connect an IP PBX to the internet without taking additional steps to secure it.

If a customer does choose to set up their own IP PBX they must ensure that it is configured securely so they do not leave themselves exposed to potentially fraudulent behaviour.

The vast majority of BT customers would never use an IP PBX in this way, so there is very little risk that other customers would experience the same issue.

Strictly speaking this isn’t entirely the HomeHub’s fault, although other routers tend to show a lot more control over traffic, even on the VoIP ports, and the wider hacks could have been mitigated had BT’s Hub done the same.

But when a customer selects to block all incoming ports then you expect that to happen, you don’t expect all incoming ports – except 5060 – to be blocked and the fact that this isn’t communicated in any way to the end-user certainly doesn’t help. On the other hand you really should get a proper router for PBX and protect the system past the hub too.