Some users reported that they have an issue when visiting our website. There are some strange subdirectories that these users are being redirected to. I have googled a lot but never found an explanation to this issue.
I have noticed that some bots such as Yandex and Bido are affected by these subdirectories.
Examples from IIS logs is as below:
Line 3065: 2016-03-28 01:36:55 10.16.16.55 GET /QYkZf/USMLg/afWLO/EN/********/NEWS - 80 - 18.104.22.168 Mozilla/5.0+(Windows;+U;+Windows+NT+6.1;+fr;+rv:1.9.2)+Gecko/20100115+Firefox/3.6 404 0 0 0 2016-03-28 02:11:06 10.16.16.55 GET /cOaOL/pYjOi/iTQZT/SSKTY/LWVVo/LlVWe/KMNSn/eoNWO/lffKo/SmKNZ/WKOXS/Ar/***/News/171-ar-17-9.htm - 80 - 22.214.171.124 Mozilla/5.0+(compatible;+Yahoo!+Slurp;+http://help.yahoo.com/help/us/ysearch/slurp) 404 0 0 15
There are many entries such as these. If more information is needed please ask.
I have read about the cockieless session state but this does not look like cookieless to me neither it is configured to use that.
We have SharePoint 2010 and windows server 2008 R2.