Most of the torrents are safe, as the well-known torrent sites check it out before hosting them for downloads. However, not all sites are safe - some may willingly distribute malware and others unwillingly attach malicious software. If a BitTorrent client is uploading from an infected computer, the are also chances your downloads may be infected.
The opinions vary on the subject of legal and illegal downloads, depending on what is being downloaded. Some sites have only legitimate content whose copyright they hold or things that are in public domain (for ex. downloading the official ISO file of a Linux distribution is legal), while many offer pirated movies, music, books etc. Checking the national law is crucial when you make an attempt to download a certain torrent. Nevertheless, BitTorrent itself is a legal technology, available to all Internet users.
Here are some opinions on why torrents can be harmful:
Torrent sites are frequently seized, and the user’s IP address and the website’s usage may be leaked by feds. One of the popular law seizing was back in July, when the authorities arrested the 30-year-old Artem Vaulin from Ukraine, the owner of Kickass Torrents, one of the most-used torrent sites on the Internet. The owner was charged with conspiracy to commit criminal copyright infringement, conspiracy to commit money laundering, and two counts of criminal copyright infringement. The court also granted the seizure of a bank account associated with Kickass Torrents, as well as several of the site’s domain names (used to host Kickass Torrents).
It is advised that the user should always use a VPN to anonymize the IP address and to protect their privacy. Just knowing the process of downloading a legal content doesn’t mean that all the torrents on the Internet are. To find legal torrents, the best thing you can do is look for them in directories that specialize in legal material of some kind, like public domain or creative common works. You can find some useful information about the sites that provide assistance in downloading legal files here:
Most of the torrent sites are linked with ads, and users are constantly bombarded with links to questionable or downright dangerous sites. Some of the ads may even contain executable scripts that can exploit browser vulnerabilities even without the user clicking the banner. Because most mainstream advertisers don’t want to be associated with torrent sites, torrent trackers are forced to turn to questionable advertisers as a source of revenue to pay their server costs. As a result, there is often very little vetting or security screening of advertisers. Many banner ads link directly to pages that will instantly try to install software on the user’s computer, or capture personal information about the user or his/hers browsing habits.
If a downloadable item is copyrighted and if the user doesn’t own it, then downloading the item for free via torrent is considered illegal. A copyright is registered to an individual or organization\company that creates something. This copyright has a time limit, usually equivalent to the lifetime of the creator and a set amount of additional years. Some copyrights are for life plus fifty years, others are for life plus seventy years. You should better check what is your country’s laws if you’re unsure of the copyright protocol. It may have a certain variation, as some things may not be protected by the law where you live, or copyright law may not be enforced at all.
Most countries have basic common laws against intellectual property theft. If a piece of music is copyrighted and the user doesn’t own it, you can’t download it for free legally. The same goes for a movie, a game or anything else. Anyway, torrent is not always equal to piracy. The torrent protocol is just a transmission mean for users to download files more easily. It is the content that makes the act illegal, not the protocol.