Flame virus scares experts as it was suspected to have been deployed for the past five years. Given this, how did Flame virus  retained its district existence for five years without any detection? What did the expert do to detect such complex virus? How can we prevent Flame virus?
Flame Virus: Most Complex Virus that Have Ever Found
I’m sorry but I think you are mistaken here. Maybe what you mean is the Flame/Skywiper virus which is a more complex type of virus instead of the Flame virus which was classified by Symantec as having a low damage level. It can easily be contained and removed as what was posted in Symantec web site.
According to them, Flame virus is only a simple floppy boot sector and master boot record (MBR) infecting virus which has a very destructive payload. The virus is activated by a change in the month starting from the date of infection. It’s a kind of seasonal virus that is only activated whenever a change in the date, the month, or the year was detected and the virus starts spreading. When your computer is infected by this virus you will see colored flames on your screen and automatically overwrites your hard drive’s Master Boot Record (MBR). It’s so destructive that you will have a loss of 1K in the total amount of conventional memory.
The other name for the Flame virus is Stamford virus. It’s not clear when this virus was detected because Symantec started updating their virus definitions December 15, 2000. You can read this virus’ full details by visiting Symantec — Confidence in a connected world.