Viruses and worms can be transferred via IM, often using file transfers, which bypass traditional anti-virus security. Some common IM clients have well-known security problems and many IM systems let users create anonymous identities which can be used maliciously.
Companies are at risk from unauthorised data leaks via IM as this is often unmonitored and messages sent aren’t stored. This makes it difficult to discover security breaches or identify the individuals responsible.
IM Spam (Spim) is an increasing problem. Spim can cause more trouble than e-mail spam, as it is more intrusive, due to the use of pop-ups, and is often of an offensive nature.