Malicious String on Site?

Hey!
I just found this on my site, and I am not sure if this is a malicius attack or something. I noticed that there was a few whois searches, and then some pages on my site got messed up. Could they have put in back door or done any other damage to our site?This is the string that I found:

host2092543910gti_binowssvidll?ul=l&ACT=4&BUILD=625&STRMDER=4&CATREQ=0
http code 404 date march 22 16:.......

Any ideas what this is?

 

 

 

 

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