This has been kicking about for several months but the Beeb has decided to bring it up. This is a particularly nasty piece of malware in that you will lose all your files it encrypts. Unlike previous version where you might be able to decrypt your files this one you can't. It's also infecting OS X machines, or some malware strain similar to it.
Most common attack vector seems to be spoofed e-mails from phone companies, banks, mail delivery companies and other trusted brand names. There are other instances of systems being attacked by drive by adverts from infected websites.
Oh and final note, always keep an offline back up of your important data.
I've came across this for someone back in middle October. Likewise I warned others at work about it immediately but it took almost 2 months before it was acknowledge as a much bigger real threat. Worst thing was it can also affect memory stick and network drives if you have it mapped to infected PC. Make sure you backup your data.
As well as having a good anti-virus/firewall that's up to date you might want to try this: http://www.foolishit.com/vb6-projects/cryptoprevent/
Whilst it can protect against malware like Cryptolocker it CANNOT save your encrypted files if you've been infected, so backup your data,then back up again, good idea to use removable media, back-up then unplug media(flash drive,external hdd)immediately if it's not connected to system it can't be encrypted as CSD said keep back-up offline.. According to National Crime Agency it's currently estimated to have infected 250,000 pc's. Symantec are saying a new B variant was discovered Monday of this week. http://us.norton.com/security_response/writeup.jsp?docid=2013-122312-5826-99
Forgot to mention make sure that if you do get Cryptolocker, insure it's fully removed from your system BEFORE restoring your files, I know this sounds obvious but it has been known to happen.