When someone downloads free 3D desktop themes from the web, there can be potential desktop themes that also install spyware on a computer. Hackers and talented programmers use any available vulnerability within the 3D desktop theme program so as to log their small program along with the downloadable file.
Once in the system, these associated spyware can poison the system and watch and record data. The spyware takes the entire control over the system and acquires all personal details and sends it to a third party. The spyware silently steals all of the user's passwords by recording keystrokes as they enter their login details or any bank PINs.
The installed spyware redirects browsers to phishing pages, keeps an eye on all the browsed pages, displays pop-ups, broadcasts personal data to distant servers and performs other secret operations without the user's knowledge. The spyware can drastically slow down and even crash a computer. The spyware does this with the owner unaware, as it does not get displayed on the Taskbar.
It is best to download the themes for a desktop from trusted and reliable sources. Some of the trusted sources include Windows Download Centre, CNET, PCMag and BrotherSoft. In addition, it is also important to install anti-spyware software and enable the firewall.