A DLL is a dynamic-link library, which are pieces of executable code that run in the background and provide additional functionality to other programs.
Generally speaking, DLL files can’t contain viruses because they don’t have any built-in methods for self-propagation.
However, a program that loads one or more DLLs can be infected with malware if it doesn’t correctly filter user input before loading the libraries.
So does this mean you should feel safe downloading a .dll file? Probably not. To keep your computer safe from external attacks, always make sure to read the accompanying information before downloading a .dll file. If you’re not sure, don’t run it.
Do .dll files contain viruses?
Yes, if they use a virus. But usually, they don’t.
Because a .dll file is a library: it helps programs or games to work better or faster. They are useful, but they can be maliciously used, too.
A malicious DLL may actually contain the code of a virus that may spread its damage all over your computer if you don’t run antivirus software on your computer.
Sometimes a .dll file does contain malware. This has to do with the fact that an infected DLL file may be included into a program at run time by some kind of Trojan / virus or other malicious programs.
Should I trust my DLL files? Can I infect my computer with a .dll file?
DLLs can be classified into two main categories: essential and optional.
Essential DLLs must be present for the operating system to function properly while optional DLLs may or may not have their corresponding application installed on a given computer.
Although it is often advised by computer professionals not to open .dll files, some malicious users have found ways of hiding viruses inside them.
This malware can be spread from the use of removable media drives such as USBs, CDs and DVDs. Once users execute a DLL file and run it without properly scanning for viruses, the program can access any drive to infect all connected devices.
The chances of encountering a virus inside a DLL file are quite high since Windows users are always encouraged to patch their OS by downloading Windows updates from Microsoft’s website. This effectively prevents viruses from wreaking havoc on systems before users have gone online to download the latest patch for their OS.
In the Windows system registry, DLL files are safely stored and used by Windows programs such as browsers and games. As long as they are secure, there is nothing to worry about.
Unfortunately, a Virus can still infect your computer if you open a malicious DLL file that loads automatically or through a security hole in your firewall.
In order to avoid exposing your computer to the risk of DLL file infection, it is always advisable to scan all downloaded files for malware before installing them.
For an added level of security, you should also link your anti-virus software program with a trusted identity management software. This way, any suspicious files will be automatically blocked from launching in your computer.
If you are using Windows 7, it is highly recommended that you disable the autorun feature and prevent access to drive letters through hidden folders. This will prevent the program from loading automatically and effectively prevent a virus from infecting your computer.
If a DLL file is not correctly installed, it is highly likely that you will find it is missing. In this case, you will have to manually install it through Control Panel > Programs and Features.
The drawback of this method of installation is that there are chances of a hidden virus being stored in the DLL file which remains undetected by anti-virus programs until you launch it.