For almost a week, Sudan has been completely cut off from the internet. It started slowly, with a series of intermittent disruptions during months of protests against former President Omar al-Bashir's 30-year rule.
Al-Bashir was toppled in April, but the protests did not end and demonstrators began demanding that the Transitional Military Council (TMC) call new elections.
On June 3, as security forces violently dispersed a protest camp in the capital, Khartoum, all mobile access to the internet was cut.
A week later, after reports of killings, rapes and other abuses began to emerge, landline access was also shut down, severing the flow of information from Sudan to the outside world.
The situation is alarming, but not unique.
As more and more people rely on the internet for everything from communication to banking, authorities around the world are increasingly switching it off.
Here, Al Jazeera explains how and why blackouts happen and the crippling effects they can have.
A blackout happens when a country's access to the internet is completely cut, preventing people from getting online.
Cyberattacks or damage to the undersea cables that carry telecommunications signals can cause this to happen, but the most common reason is that authorities choose to turn off access.
Deliberate internet blackouts by authorities have been recorded as far back as 2005, but the practice became more widely-known after Egypt's week-long government-imposed blackout during its 2011 uprising.
In countries where traditional media is tightly controlled, the free flow of information online can be seen as a threat to authorities.
Limiting or completely blocking access is one tool they can use to control both citizens and the narrative around an event.
Authorities use national security and public interest concerns to justify the blackouts, which often occur in times of panic or potential instability.
Social media was temporarily blocked in Sri Lankafollowing the Easter Sunday bombings to prevent the spread of rumours, while internet access has been disrupted in a slew of African countries during recent elections in attempts to limit the influence of social media on the polls.
However, according to Alp Toker, executive director of Netblocks, an NGO monitoring internet censorship, these justifications can sometimes mask more sinister aims.
"We've seen that shutdowns are used to cover up incidents that are embarrassing. [They] are used to cover up violations of human rights, including alleged reports of killings," he said.
Critics of internet censorship also note the frequent overlap between blackouts and anti-government protests as evidence that blocks are being used to silence dissent and make it difficult for citizens to organise large protests.
Authorities have also imposed blackouts during nation-wide exams in Iraq and Algeria, as well as Ethiopia, where the internet was blocked for four days this week. The measure is necessary, authorities say, to prevent students from cheating.
To disrupt the internet, authorities must order internet service providers (ISPs) to limit access for their subscribers.
Toker told Al Jazeera that while some ISPs - which are often state-owned - readily comply with these orders, others have reportedly been held at gunpoint and forced to switch off the internet.
These orders are often made in secret and carried out by ISPs on an individual basis, meaning companies can sometimes choose which kind of filter to apply.
Aside from a total blackout, content blocks and "bandwidth throttling" can be used to to limit internet access.
China regularly imposes blocks during anniversaries of the 1989 Tiananmen Square protests [File: Andrew Wong/Reuters]
In a content block, access to certain websites or apps is cut. This is frequently used to shut down social media, but has also been applied to news sites and other sources of information like Wikipedia.
China recently tightened its online restrictions ahead of the 30th anniversary of the Tiananmen Square protests in early June by blocking access to the sites of international news organisations including CNN and Reuters.
Bandwidth throttling is a more subtle approach, in which signals are made so weak and connections so low that the internet is effectively unusable.
"People will generally blame their own connection," Toker said. "It's quite difficult to take that leap and realise it's also the rest of their street, it's also their city, it's their country. This means that throttling and partial restrictions on services can be used to cover up mass censorship".
Content blocks and bandwidth throttling often come before a total internet blackout.
The most popular way to bypass restrictions is with a virtual private network (VPN, which masks a user's location, making it seem as though they are in another country and so evading blocks on specific sites.
Authorities can block VPNs but backlash from foreign diplomats and companies that use them means this rarely happens.
In a total blackout, however, accessing the internet is almost impossible.
The fallout from an internet blackout can be catastrophic and far-reaching as people's daily lives become ever more entwined with the online world.
Blackouts make it harder for protesters to organise rallies and voice dissent [File: AP Photo]
Political - The most obvious impacts are political. Stemming the flow of information in and out of a country can throw reports of atrocities into doubt, making it difficult to mobilise the international community.
In Sudan, the blackout has hampered efforts by rights groups and journalists to verify the death toll following the June 3 crackdown or subsequent reports of human rights abuses.
Without access to social media, protesters cannot easily organise mass rallies or voice their dissent. However sometimes, blackouts can have the opposite effect and actually draw attention to the very issues they were put in place to smother.
In the case of Sudan, the country's large diaspora took to social media to slam the blackout and support protesters. Their messages have been picked up by celebrities, including model Halima Aden, and international rights groups, putting the crisis in Sudan in the spotlight.
Economic - Internet blackouts can do severe damage to a country's economy by limiting people's access to banking and preventing businesses from contacting each other.
Dawit Bekele, Africa bureau director at the Internet Society, an online standards monitor, blackouts also deter much-needed investment.
"Investors need the internet to come to a country, when they see that a government is shutting down the internet, they think twice before going there," he told Al Jazeera.
Netblocks estimated that the four-day shutdown in Ethiopia last week cost the country $17m, while a 2016 report by the Brookings Institution, a think-tank, said the global economy lost $2.4bn through internet shutdowns between 2015 and 2016.
Social - Disruption to the internet can wreak havoc on people's daily lives and even be a matter of life and death.
"We've tracked cases where women have miscarried because the couldn't get to hospital on time during shutdowns," Toker said.
"We've spoken with people who have lost friends and family and they still aren't able to get in touch because of the pandemonium these acts of censorship have caused."
Transportation is affected during a blackout, making it difficult for people to get to hospital [File: Mohamed Nureldin Abdallah/Reuters]
Human Rights Watch reported this week that under the blackout, Sudanese people were unable to get updates about roadblocks or makeshift medical centres, putting lives at risk.
Bekele told Al Jazeera that, during an internet blackout in his own country, Ethiopia, he was unable to bring important medicine into the country for a friend because he could not make contact with him to find out the prescription.
"I'm sure there are thousands of these types of situations because today we depend on the internet for our daily lives," Bekele said.
Despite the damage they cause and a patchy success rate, internet blackouts show no signs of losing popularity.
The United Nations declared internet access a human right in 2016, but while the UN can send monitors to countries and raise awareness of internet restrictions, the body has little power to prevent authorities from imposing blackouts.
Last year, there were 188 shutdowns, according to Access Now, a monitoring group, up from 108 in 2017 and 75 in 2016.
"It does seem there's a contagion," Toker said. "Countries learn from each other and once they see that one neighbour gets away with it, countries try to do the same thing."
Sudan's public prosecutor has charged jailed former President Omar al-Bashir with corruption, according to state media. Al-Bashir was overthrown and arrested in a coup by the military on April 11 after months of mass protests against his 30-year autocratic rule. The SUNA news agency on Thursday quoted an official source as saying that al-Bashir "had been charged under foreign exchange possession materials, the heinous and suspicious wealth and emergency orders".
Protest campaign will continue until military transfers power to civilian government, organisers say. Sudanese police have fired tear gas at protesters taking part in a "civil disobedience" campaign, called in the wake of a deadly crackdown on demonstrators, that began on Sunday. Protesters gathered tyres, tree trunks and rocks to build new roadblocks in Khartoum's northern Bahari district, an unnamed witness told AFP news agency, but riot police swiftly moved in and fired tear gas to disperse the crowd. "Almost all internal roads of Bahari have roadblocks. Protesters are even stopping residents from going to work," said the witness.
Sudan’s military has used live ammunition to disperse protesters in the capital, Khartoum, according to reports. A medical association close to the protesters said that at least 13 people have been killed and dozens injured. Sudan has been ruled by the Transitional Military Council since the ousting of authoritarian president Omar al-Bashir in April. The crackdown comes as participants in a long-running sit-in outside the army’s HQ have been demanding democratic reforms and for generals to hand over power.
Here's more from the statement by Sudan's Minister of Defense, Awad Mohamed Ahmed Ibn Auf. He confirmed that President Omar al-Bashir had been forced from power and his government dissolved after months of demonstrations calling for his ouster. A two-year military council has been established to oversee a transition of power, ending Bashir's three decades of rule. The defense minister said that Bashir had been forcibly removed and was now being "kept at a safe place."
Sudanese President Omar Al-Bashir yesterday called for forming a new government “capable of tackling local issues and meeting citizens’ needs.
Sudan President Omar al-Bashir, facing the country’s biggest popular protests since he came to power 30 years ago, declared a one-year state of emergency on Friday and called on parliament to postpone constitutional amendments that would allow him to seek another term in a 2020 presidential election.
Sudan announced that it had released some 2,430 protesters from custody yesterday, as US officials warned that the violent crackdown on demonstrators threatens Sudan’s removal from Washington’s terror blacklist.
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