With all the panic over the last week with the first http://www.symantec.com/security_response/writeup.jsp?docid=2011-061615-3651-99BitCoin Trojan;, BitCoin wallet theft and such (think “Information superhighway robbery :P ), I thought it best to ease some folks into backing up thier wallets.
First, it is unwise to surf the internet on a machine with your BitCoin client’s wallet on it (more so if you use Windows). Second, there are many ways to encrypt and obfuscate a file that it makes little sense to take no action. That part is up to you, although hopefully it will be easier to secure in future versions of the BitCoin client. The most you’ll need to know is that the file you need to back up is wallet.dat. The location of this file is as follows:
C:\Documents and Settings\[USERNAME]\Application Data\Bitcoin\wallet.dat
Windows Vista & 7:
/Users/[user]/Library/Application Support/Bitcoin/wallet.dat [unverified]
Other possibilites include running nothing but a BitCoin client in a Virtual Machine, such as VirtualBox, or VirtualPC (which is free to use from Microsoft). In this case, you could run the client with nothing but a LAN host adapter.