Downloading photos from the Internet will probably not harm a computer because image files contain no executable code, thus making it virtually impossible for a virus to hide inside a picture. Viruses can sometimes appear to be image files by using double file extensions such as “file.jpg.exe,” and some image hosting websites may also contain malware. Users should also be aware of copyright law when they download photos for personal or commercial use.
Computer files can contain either executable code that runs as a program or static information meant to be read by other software. Image files fall into the latter category and were not designed to contain executable code. Since computer viruses, worms, and other forms of malware run as executable programs, it is unlikely that someone trying to download photos would be placing his or her computer at risk. It is at least theoretically possible for an attacker to create a deliberately damaged image file that would crash or manipulate the program opening the file, but this type of attack is very rare.
A more significant threat comes from executable programs masquerading as image files, a tactic used by some virus and malware authors to disguise their malicious creations. One virus that was particularly effective at this type of deception spread through e-mail messages with an attachment named “AnnaKournikova.jpg.vbs.” Although the filename contained “.jpg,” i.e, a valid extension for an image, the actual file extension was “.vbs,” an executable format. As a result, anyone who tried to download photos of the Russian tennis star was actually opening a virus that went on to mail copies of itself to each entry in the user’s address book. True image files will only end in “.jpg,”, “.gif,” or “.png.” All other extensions should be avoided.
Some websites that offer the ability to download photos may covertly attempt to install malware or spyware on a user’s system. These sites might be set up with the intention of targeting visitors or might be legitimate sites that have been hacked. Common sense security precautions such as keeping software up to date can help alleviate the risk of malware infection.
Even if they are found through a search engine or displayed on a public website, it is also important to realize that pictures on the Internet may be protected by copyright law. Downloading these photos for a school presentation, sharing them with friends, or using them on your own website could be a form of copyright infringement. It is especially important to determine the copyright status of an image if it is going to be used for commercial purposes. Some websites publish content under a less restrictive license that allows users to download photos for certain uses. A search for “Creative Commons” or “public domain images” can help keep users out of hot water.