For feature on spy gadgets in Verve magazine. Secret Agent Pen, R1 155 from, showing where the USB flash stick is hidden.

Berlin - When a computer virus strikes, should you install new virus protection or wait until problems manifest themselves?

The best solution? Find special scanner software from which you can boot up a system so it can be searched through and cleaned up. As a bonus, some of these options are free.

Examples of such software include the BitDefender Rescue CD or the Kaspersky Rescue disc. Both can be downloaded for free as ISO files and burned as a memory map volume. Using standard Windows tools, you can get the file with a simple click.

There's also the option of saving the Kaspersky ISO data onto a USB stick. The manufacturer offers the perfect complement for that option: the USB Rescue Disk Maker. The tool has to be opened through a contextual menu with administrator privileges. Data already saved on the stick is kept safe.

The tool installs a boot sector on the stick and integrates the necessary data for a rescue CD. This usually means about 200 megabytes (MB) of data.

Other free rescue CDs available are the AntiVir Rescue CD, the F Secure Rescue CD or the AVG Rescue CD.

“It's important to start up the computer with the boot CD/DVD of an anti-virus programme and not to go looking for viruses with your current operating system,” says Wolfgang Hosbach, editor with the German publication PC Magazin.

That's the only way that so-called rootkits can be found, which might have taken root on the hard drive. If you're dealing with a truly tough virus, it's best to use a series of rescue CDs one after another, advises Hosbach.

If this doesn't find the problem, then the whole computer has to be rebooted. “That's not the worst solution,” says Hosbach. “Data can be resurrected with a Live Linux system, also started off a CD, onto an external USB drive.”

Freeware Sardu can be used to set up a multiboot USB stick that holds multiple virus scanners, just with a few clicks in the assistant programme. Users just need to use the right rescue CD to load the tool.

There are also a host of Linux Live systems like BackTrack, Fedora or Ubuntu that can be integrated. When doing so, use the progress bar or the report function to check the current status. On the right, a display shows how big the multiboot system is. If all ISO files have been downloaded, then the stick onto which the system should copy the data can be searched, just by clicking Search USB.

Users can then use the stick to boot up a computer and use the scanners to check the system. If you do boot up a computer via USB, then it's often necessary to fix certain settings in BIOS or to call up the boot menu while the system is starting.

The multiboot stick can also be used to check the computer regularly with the various rescue discs. After all, it's always possible that a virus or a worm might go unnoticed during regular operations.

Windows Defender Offline Beta lets users of Windows PC have a graphical interface when using its rescue CD. But be careful, because it's easy to accidentally damage the entire operating system.

“A virus problem in a computer is definitely not trivial. The user cannot always remove the damage by himself,” says Christian Meyer, chief editor of the IT web portal ChannelPartner. Do-it-yourself repairs can quickly lead to a complete loss of all data. “Especially if you're dealing with critical and sensitive data, you should get an expert.”

However, there are options, like Microsoft Safety Scanner, for running checks with an operating computer. - Sapa-dpa