Kingsley FAQ's - internet access, adsl and Broadband solutions, website hosting.

An ADSL account may contain extraneous or unexplainable usage on the stats page.

There are a number of causes of unwanted traffic:

Causes
Network chatter
Up to 10mb per day of random packets caused by portscans, dns, router update checks, remote pings etc. This will occur even if your PC"s are switched off if you have a router as opposed to a USB based ADSL modem.

Skype
New Skype client generates traffic even if not in use. This is because skype can turn any PC into a 3rd party router for assisting in its P2P telephony functioning.

Stolen username
Their are known exploits and hackers actively scanning insecure routers to obtain usernames and passwords. These are then used to steal bandwidth from the account.

Wireless hijacking
If your router is wireless enabled, hackers in the nearby vicinity may be using your bandwidth for their own purposes, even if WEP or WPA is enabled.

Spyware,malware,viruses,trojans, rootkits
Any of the PC"s connected may be infected with the above causing your machine to become a zombie for sending spam or an instrument in sending denial of service attacks. New evidence suggests rootkit technology is now being employed to avoid detection by most Antivirus programs.

olutions

Network chatter
Turn of your router to avoid any traffic charges. Alternatively put the router in "stealth mode" - this makes it appear to be offline to the outside world and reduces the small amount of daily wastage.

Skype
Log out of Skype when not in use. Use a different client, eg MSN Messenger or other SIP based voice services.

Stolen username
1) Change all passwords - adsl password, router password, client service area password etc...

Wireless hijacking
Enable WPA-PSK encryption using a 12+ character random password. Do not use known words, product names, labels or anything else. Do not use WEP encryption as this can be cracked within minutes giving a false sense of security.

Spyware,malware,viruses,trojans, rootkits
Run multiple virus and anti spyware scans on your system, there are various tools available to do this via the web:
Trendmicro Housecall
Panda Active Scan

There are also various tools available to track traffic usage on individual PC"s, the easiest to use is probably Netlimiter:
NetLimiter

NB:
Please also see these password guidelines to ensure the passwords you have selected are adequately secure:
http://security.fnal.gov/UserGuide/password.htm
http://www.newsforge.com/software/03/02/26/1639212.shtml?tid=2