Please help with rule

[Dave Koontz]

I am still getting some Storm Worm messages that are not being caught, 
even with Sane Security / ClamAV.  I thought I'd write a rule to score 
any URL that has a dot exe, scr or pif extension.  However, my rule is 
not working.  Can someone help advise what is wrong?  I want it to 
pickup any http or https with those extensions.

body     Dangerous_URL        /http{1,200}\.(?:exe|scr|pif)/i
describe Dangerous_URL        Dangerous URL
score    Dangerous_URL        7.5

Thanks in advance!