Got a BTHomeHub version 1.0 or 1.5? It uses WEP (Wired Equivalent Privacy) for its wireless encryption as standard - but that's now very insecure. The latest Home Hub 2.0 defaults instead to the WPA (wi-fi protected access) security protocol, which is much more secure (see my separate networking post for why you should secure your wifi, and more on wifi security).
Even if you have a cable connection from your computer to your Home Hub and you don't use it to connect to the internet wirelessly from another computer in your household, the wireless feature of the HomeHub is turned on by default - so you still want to make sure it's as secure as possible to ensure that other people (neighbours, people in the street) don't use your broadband connection for their own purposes, which could eat into your download/upload quota, and so cost you money, as well as potentially lay you open to being held responsible for things they do online, like downloading illegal material (again for more info see the security section of my post on wifi networking).
To try to stop this wifi leeching by others, the Home Hub does provide wireless security by using a secure encrypted connection for wifi which requires entering a key (password) on a device before it can connect to the Hub - but earlier versions use the now no longer very safe WEP encryption.
If you have an older version of BT's HomeHub (and if you first started using BTBroadband as your ISP or internet service provider more than a few months ago, you probably do), then using WEP is a security risk for you and your family, and you ought to secure your wireless network properly by changing it to WPA if you haven't already - unless you need to retain WEP because a computer or device in your household which needs to connect to the internet via the router is older still and only supports WEP, not WPA. (In that case, you're still better off trying to upgrade the computer's wireless adapter so that it supports WPA, instead - a USB wireless adapter doesn't cost much these days and it's probably worth it - see section 2 of my previous post for more info.)
BT did put out a note about this back in April 2008 on their service status webpage -
- but honestly, how many customers visit that page regularly or indeed at all? (there's not even a feed for their status updates). BT really should have sent an email out to its customers about that, I feel.
How to change BT Home Hub version 1.0 from WEP to WPAInstructions for the different versions of BTHomeHub are linked to from the BT Home Hub security advice page - the info on how to change security from WEP to WPA is the same for both 1.0 and 1.5 - so follow those links, I won't go into that here.
See my previous post for more on wifi networking in your home and other security measures.