Maintaining anti-virus defenses and never opening questionable attachments are important practices for any user - from the home through the largest enterprise. However, this is a message that gets lost on many, given the ease with which new viruses proliferate.Even with the best defenses and practices, new virus strains sometimes sneak past and can damage or destroy data on an individual hard drive or a network server. While a number of viruses are fairly innocuous, many are malicious in nature and can wreak havoc on your PC or network.Ontrack has published some common-sense guidelines on what to do after a virus has infected your PC, guidelines that can help you or a data-recovery service recover damaged or lost data. Among their suggestions:* If you\u2019re attached to a network, physically disconnect the infected computer from the network so that it can\u2019t spread the virus.* If you find that data is missing due to a virus or suspected virus, turn off your Windows-based computer instead of going through the normal shutdown procedure.* Don\u2019t continue to use the potentially infected machine for Web browsing or other activities, since continued activity can overwrite data that a virus has deleted.* Defragment often, since this keeps files more organized and improves the potential for recovering lost data.I would add to this list two more things. Implement and deploy good anti-spam defenses, since the line between spam and viruses is continuing to blur. And implement tools that can either block unprotected consumer-grade instant messaging traffic in an enterprise setting or, better yet, implement good defenses for your consumer-grade IM infrastructure that can block viruses and rogue protocols.Even better than that, at least for enterprises, is the use of a multi-faceted service that offers protection against a variety of e-mail and IM-related threats, not just spam or viruses.