One of the major concerns about downloading free content is its harm potential. Once the soft wares are downloaded, the computer gets infected. It is therefore important to prevent, detect and remove viruses to secure a system. There are many ways you can check whether downloaded software is secure to install and use.

Install an anti-virus program
Anti-virus software such as Norton is the surest way of securing your computer.

• The software gives you an alert every time a virus has been detect and blocks it.
• The anti-virus also helps remove a detected virus.
• If downloaded software has been blocked, then it is not secure to install on your computer.
• Notifications help, shield the computer against harmful content.

Overall system behaviour
When insecure software is installed and run on a system, embedded virus is injected into the computer system.

• The virus will generally slow down your computer. When this happen, it is time to run a scan.
• Uninstall the recently installed software and note the change.
• A virus will most likely make changes to your computer like creating shortcuts, shutting down etc if this happens, run a system check. The computer could be infected.
• Secured systems will present an error message when a virus or harm has been detected.

Legitimacy
Legitimacy goes hand in hand with security. Legitimate software will in most cases be secure software.

• Check the downloaded software details, its authors and manufactures.
• If some of the details are missing or unknown, do not download or install the software. Legitimate software should have a known author. Missing authors can be an indication of a virus.
• The type of the software can also help check its harmfulness, most free downloads of music, movies etc are mostly likely harmful.
• Always download your contain from trusted sites. Most sites are known to be providing software for ages; most of their software is bound to be legit.
• Check the file extension. If it is an executable file (.exe), it’s most likely harmful
• A legit download will always bring up a pop up window to show the download details. If it does not happen, ignore.

Others
there are other several tips that can help detect security of downloaded software.

• Forums and reviews are important aspects of software. Good free software should have positive reviews and comments from people who have already used it.
• If the reviews are negative do not use.
• Check for the software information and details from sites like Google and WHOIS. The information you get can help decide on software.
• Do not follow a download link from an unknown email attachment.
• Sometimes common sense just work, If your instinct tells you a software is not right, do not ignore.
• Never trust a download that requires your personal information.

When some of the free software is legitimate and genuine, most are just carriers of hidden embedded viruses. There are mostly targeted to unsuspecting individuals. Preventing virus from probably insecure software is an important principle. It is always a good decision to install anti-virus software. Most come with helpful tips and advice on keeping your computer secure.
For instance Norton antivirus support provides an extensive support on downloads, technical errors, tools for eliminating viruses and help on virus removal