Iran Shuts Down Internet: How Governments Can Switch Off an Entire Nation’s Connectivity

Tehran: Amid escalating protests, Iran has once again plunged into a near-total internet blackout, cutting millions of citizens off from the digital world. Such shutdowns raise a crucial question: How can a government bring the internet of an entire country to a halt in one stroke?

Experts say governments across the world rely on a few powerful technical methods to restrict or completely block internet access during times of unrest. The most commonly used techniques are routing disruption and packet filtering.

Routing Disruption: The Most Effective Weapon

The most drastic and effective method is routing disruption. In simple terms, the internet functions through interconnected networks known as Autonomous Systems (AS), which are typically controlled by Internet Service Providers (ISPs) or large organizations. These systems exchange information using a protocol called the Border Gateway Protocol (BGP).

When an ISP, under government direction, withdraws its BGP routes from the global routing table, the IP addresses it controls effectively disappear from the internet. As a result, other networks around the world can no longer reach those IP addresses, instantly cutting off internet access for users connected to that provider.

In practice, this means that smartphones, computers, and servers inside the affected region are unable to send or receive data from outside networks. When multiple ISPs do this simultaneously—as often happens during nationwide shutdowns—the entire country can go offline within minutes.

Packet Filtering: Targeted Internet Control

Unlike routing disruption, packet filtering is usually applied in a more selective manner. Instead of blocking the entire internet, this technique is used to restrict access to specific websites, apps, or online services.

Governments can instruct ISPs to block data packets associated with certain platforms, such as social media sites or messaging apps. In recent years, many countries have also adopted Deep Packet Inspection (DPI) technology. DPI allows authorities to examine the contents of data packets in real time and block specific types of information or communication, rather than shutting down connectivity altogether.

Why Governments Choose Full Shutdowns

While packet filtering allows for partial control, experts note that during large-scale protests or political crises, governments often resort to routing disruption. This method is faster, harder to bypass, and far more effective in preventing communication, coordination, and the flow of information.

Iran’s current internet shutdown follows this pattern, highlighting how modern states can exert near-total control over digital infrastructure during periods of instability.