index.html definition, relationships, removal:

PC Activity Monitor is an essential part of a particular parasite and therefore is responsible for the pest's malicious activity. Exact purposes of index.html depend on the related parasite's type and carried payload. Some threats can use index.html to serve annoying pop-up advertisements or store certain configuration settings, while others need it to corrupt files, steal user confidential information or run a spreading routine. In any case, DO NOT open this file!
The index.html file is installed and used by keylogger Hooker Trojan Keylogger. It is also related to other parasites such as keylogger Japanese Key Logger, keylogger PC Activity Monitor, keylogger Probot, BirdSpy 3.0, GayOL, IWAnywhere 1.0, Red Spider and EasySearch. These threats can use index.html for different purposes, as the file's functionality depends on a particular parasite it belongs to.
Sometimes a presence of index.html does not indicate that your computer is infected. It can be an essential system file or a file installed by harmless legitimate software and therefore may not pose any threat to your privacy and the system. Although such cases are quite rare, you should thoroughly examine index.html before completely deleting or leaving it in the system.