We've seen a pattern in our webserver access logs which we're having problem explaining. A GET request appears in the access log which is a legitimate, but private, url as part of normal e-commerce website use (by private, we mean there is a unique key in a url form variable generated specifically for that customer session). Then a few seconds later we get hit with an identical request maybe 10-15 times within the space of a second. The duplicate requests are all from different IP addresses. The UserAgent for the duplicates are all the same (but different from the original request). The reverse DNS lookup on the IPs for all the duplicates requests resolve to the same large hosting company. Can anyone think of a scenario what would explain this? EDIT 1 Here's an example that's probably anonymised beyond being any actual use, but it might give an idea of the sort of pattern we're seeing (it's from a search query as they sometimes get duplicated too): xx.xx.xx.xx - - [21/Jun/2013:21:42:57 +0100] "GET /search.html?search=widget&Submit=Search HTTP/1.0" 200 5475 "http://www.ourdomain.com/index.html" "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)" xx.xx.xx.xx - - [21/Jun/2013:21:43:03 +0100] "GET /search.html?search=widget&Submit=Search HTTP/1.0" 200 5475 "" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_7) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.91 Safari/534.30" xx.xx.xx.xx - - [21/Jun/2013:21:43:03 +0100] "GET /search.html?search=widget&Submit=Search HTTP/1.0" 200 5475 "" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_7) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.91 Safari/534.30" xx.xx.xx.xx - - [21/Jun/2013:21:43:04 +0100] "GET /search.html?search=widget&Submit=Search HTTP/1.0" 200 5475 "" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_7) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.91 Safari/534.30" xx.xx.xx.xx - - [21/Jun/2013:21:43:04 +0100] "GET /search.html?search=widget&Submit=Search HTTP/1.0" 200 5475 "" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_7) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.91 Safari/534.30" xx.xx.xx.xx - - [21/Jun/2013:21:43:04 +0100] "GET /search.html?search=widget&Submit=Search HTTP/1.0" 200 5475 "" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_7) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.91 Safari/534.30" xx.xx.xx.xx - - [21/Jun/2013:21:43:04 +0100] "GET /search.html?search=widget&Submit=Search HTTP/1.0" 200 5475 "" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_7) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.91 Safari/534.30" xx.xx.xx.xx - - [21/Jun/2013:21:43:04 +0100] "GET /search.html?search=widget&Submit=Search HTTP/1.0" 200 5475 "" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_7) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.91 Safari/534.30" xx.xx.xx.xx - - [21/Jun/2013:21:43:04 +0100] "GET /search.html?search=widget&Submit=Search HTTP/1.0" 200 5475 "" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_7) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.91 Safari/534.30" xx.xx.xx.xx - - [21/Jun/2013:21:43:04 +0100] "GET /search.html?search=widget&Submit=Search HTTP/1.0" 200 5475 "" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_7) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.91 Safari/534.30" xx.xx.xx.xx - - [21/Jun/2013:21:43:04 +0100] "GET /search.html?search=widget&Submit=Search HTTP/1.0" 200 5475 "" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_7) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.91 Safari/534.30" UPDATE 2 Sometimes it is part of a checkout flow that's duplicated to I'd think twitter is unlikely.