2019 is already a busy year for internet shutdowns in Africa, with governments ordering cutoffs as soon as a crisis appears."It is not even the second month of the new year and we have had significant internet shutdowns in four African countries," said Berhan Taye, who leads the #KeepItOn campaign for global digital rights group Access Now. The group noted 21 shutdowns across Africa last year and 13 in 2017.Zimbabwe ordered a "total internet shutdown" last week during protests over a dramatic fuel price increase and a resulting deadly crackdown. The Democratic Republic of Congo late on Saturday restored internet service 20 days after the disputed presidential election, as a court moved to declare the winner. Gabon shut off service during an attempted coup, and Sudan earlier blocked social media amid growing calls for its longtime president to step down.How do governments do it? Here's a quick guide.TURNING IT OFFGovernments tell internet service providers, some of them government-owned, what to block. The fewer ISPs, the more easily it's done. "One tool available to governments that makes shutdowns so frequent are the contracts ISPs sign with the communication regulator," Taye said. "In this contract, there is a clause that gives the communication regulator the power to order service providers to restrict access to the internet or block social media apps at the regulator's request. These clauses usually indicate that regulators can order shutdowns in times of national security or public safety concerns, but these phrases are seldom defined and narrowed down in these contracts."In Zimbabwe, the country's largest telecom company, Econet, has been sending customers text messages relaying the government's orders and calling the situation "beyond our reasonable control." A media group and the Zimbabwe Lawyers for Human Rights have petitioned the High Court in the capital, Harare, arguing that the government has "no legal basis" for such orders. A hearing is on Monday.TARGETING HERE, TARGETING THEREShutdown methods vary. Internet service providers can alter routing information at key infrastructure points so traffic is blocked, notably to the world beyond a country's borders. "This is often the mechanism used to take a whole nation offline," Taye said. Filtering apps, a popular tool, can be used to block access to selected social media. Various forms of "throttling" can be used to make a service appear unavailable, frustrating users who don't know whether the problem is technical or deliberate. Domain name servers can be manipulated to send traffic away from intended destinations and toward servers controlled by the government.The Zimbabwe government has defended its actions, calling the internet shutdown necessary and asserting that people had used online platforms to co-ordinate the unrest and threaten society. "There is no way that you expect us to sacrifice a national good for the sake of the internet," presidential spokesperson George Charamba said on Saturday night on state television.IT GETS COMPLICATEDAs it becomes clear a shutdown has occurred in a country, residents quickly look for workarounds. In DRC, people in the capital, Kinshasa, found ways to tap into services provided just across the Congo River in the Republic of Congo. Others in the east of the sprawling country moved toward the borders with Rwanda and Uganda to pick up coverage options offered in those countries. And in Zimbabwe and elsewhere, a brisk flow of information began about which virtual private networks, which mask a user's location, were the best to use to get around controls. In Sudan, some activists are using VPNs because internet service, while not severed, has slowed during the unrest.Activists say African countries are only hurting themselves and their economies. Zimbabwe's shutdown has cut off crucial access to the electronic bank deposits that the struggling government, without a national currency, uses to pay teachers and other public workers. Electronic remittances from the millions-strong diaspora have been affected. Local media have reported that the shutdown is costing the country millions of dollars it cannot afford.The NetBlocks civil society group that documents internet disruptions around the world says it is working on a tool to better measure their cost to countries and their people.