A law banning VPNs, or virtual private networks, goes into effect today in Russia as part of President Vladimir Putin’s latest hamper on internet freedom.

Signed by Russian President Putin in July, the bill obliges Internet providers to block websites that offer virtual private network services. A popular use of VPNs in Russia is to circumvent blocked content online by rerouting one’s connection through a completely different originating country. Russia’s latest step in cracking down on blocked content comes as the Russian government looks to simultaneously increase storage of companies’ private user data on their own servers.

This latest anti-VPN move by the Russian government was pushed by authorities and legislators who cited concerns of extremist or terrorist materials online. Russian authorities claim that extremist content can easily circumvent law enforcement tactics by routing their server through outside countries.

VPNs have become considerably more prominent in the past few years, particularly in countries under the thumb of oppressive regimes known to censor content or shut off the internet entirely to prevent access. VPNs are gaining popularity all over as internet users become more aware of just how much everyone from prying government eyes to massive tech corporations are able to learn about people’s daily internet activities with such ease.

As International Business Times has previously laid out, a VPN is a privacy tool that enables a device to send and receive information across a public network as if it was connected directly to a private network. It obscures the true location of a device and makes it appear as though its activity it coming from a separate network. It’s often compared to a sort of firewall for your online activities.

When a person connects to a VPN, it creates an encrypted and secure connection between the user’s device and a remote server.  Any information, including that from web activity to user information to passwords, is sent first through that encrypted connection.