Win32/SillyDl.DUI is a downloading Trojan.

Win32/SillyDl variants may be installed via Internet Explorer exploits when users visit malicious web pages; other Trojan downloaders or components; or they may be packaged with software that the user has chosen to install.

A downloader is a program that automatically downloads and runs and/or installs other software without the user's knowledge or permission.

In addition to downloading and installing other software, it may download updated versions of itself.

Win32/SillyDl variants may download other Trojans, or non-malicious programs such as adware. At any given moment in time, the program(s) it attempts to download may be changed or updated, or may be unavailable altogether. This family of Trojans usually downloads using HTTP.

In order to avoid SillyDl infections it is important to follow safe computing practices, such as keeping your Operating System and third party applications up to date and patched with the latest updates, and use an Anti-Spyware and Adware solution such as CA Anti-Spyware.

More information can be found at this Proland Software page.