Experts in field of computer security warn about new error in operational system Windows. Viruses, which use this error, are of potential treat for millions of personal computers, working in any version of operational system released since 1990. Mistake in operational system was revealed last week by hackers. It allows to infect computers by virus code, placed in image file. The threat of massive attack increased by several times after group of hackers has published original code of virus this weekend. Unlike the majority of harmful programs, which demand downloading and running of suspicious file on computer, new virus can infect computers while viewing of web-pages, e-mail and others. Microsoft corporation knows about the mistake but there is no official update to correct it. Experts of corporation advise to be careful while opening the e-mails or hyperlinks, received from unknown sources. Meanwhile several experts advise to install unofficial update, developed by Russian programmer Ilfak Gulfanov. The patch is placed on personal Internet-diary of the programmer and on sites of anti-virus companies. Despite the fact that correction of Gilfanov was approved by several anti-virus companies, many organizations announced that installation of unofficial code is unacceptable for them.