Fraudsters use personal information from different sources to steal people's identities. Viruses are one way to do it. But they also use paper documents of your accounts containing personal details, such as receipts and bank statements.
Fraudsters use many methods such as searching dumped financial documents in dustbins, unattended documents left on desks or somewhere to obtain useful information about you and your banking history.
You should take simple precautions to keep your details safe and to dispose of these documents safely, such as shredding them before you bin them.