Lima and her friends in Tehran fear arrest, beatings and even death by joining mass protests demanding more rights and a new leadership in Iran. But a yearning for change and a kit bag of tech, from mobile apps to encrypted chat, have kept them going.

Struggling to suppress the biggest show of dissent in years, Iran's authorities have also turned to technology, using delivery apps, Twitter and facial recognition to track protesters, eavesdrop on opponents and harass women who defy their strict dress code, rights campaigners said.

That has made technology a "double-edged sword in the protesters' fight for freedom", said Azin Mohajerin, lead human rights officer at Texas-based Miaan Group, which supports rights organisations in Iran.

Iran's Ministry of Information and Communications Technology did not respond to a request for comment.

Lima, a 23-year-old student who did not want to use her full name, uses a virtual private network (VPN) to access banned sites as she takes to the streets, all the while checking social media and messaging apps to dodge the security forces.

Data shows a 1,000?ily increase in the number of Iranians signing up for VPNs to stay under the radar in the crackdown.

Lima also relies on Gershad, a crowdsourced app that lets users share and track the real-time locations of morality police who can harass or detain women for "inappropriate dress".

"We use the app because we're scared," said Lima, who has used Gershad about a dozen times in the past five months.

"We've managed to change direction and dodge the morality police several times only because of the app," she added.

Iran has been gripped by protests since the death in September of a 22-year-old Kurdish woman, Mahsa Amini, in the custody of the morality police. In response, authorities have cracked down with force, imposing internet shutdowns and blocking social media platforms to stem the flow of information.

Gershad was created in 2016 by a human rights nonprofit - United for Iran - with the aim of supporting women in Iran.

It is among several tools favoured by journalists, activists and other Iranians as authorities step up digital surveillance in a bid to quell the anti-government protests among a young and increasingly frustrated population.

Gershad has had some 86,000 downloads and many users have used it to dodge the morality police, with protesters repurposing it so they can also report the whereabouts of riot police, said Firuzeh Mahmoudi, executive director of United for Iran.

"There is a need to support Iranian women as they are being persecuted and oppressed by the morality police," she told the Thomson Reuters Foundation by phone from San Francisco.

"This is also a sensitive app, so some people are removing it from their phones when they go out, and instead use social media to report and view the location of security forces. But if the internet is shut down, then all bets are off," she said.

SAFE TOOLS
Iran was one of the countries with the highest number of internet shutdowns last year, with authorities pulling the plug regularly this year to clamp down on the new dissent, and prevent protesters sharing footage of any police violence, human rights groups say.

The activist HRANA news agency said 318 protesters had been killed in the unrest as of Saturday, including 49 minors. While government officials have not provided their own estimate, state media said last month that more than 46 security forces members, including police, had been killed.

Authorities say Amini had health issues, and have blamed foreign enemies and their agents for the unrest. Officials have said they will hold public trials of about 1,000 people charged over the protests in Tehran.

As security forces crack down on women defying the dress code and increasingly calling for new leadership, tech experts have cited Iran's covert campaign of digital surveillance as a key threat and urged demonstrators to arm up in defence.

"A lot of these young people getting arrested, getting killed, are high school or college students and don't have the knowledge on how to be secure online," said Sussan Tahmasebi, founder of Femena, a rights organisation in Washington, D.C.

U.S. authorities in September issued guidance expanding the range of internet services available to Iranians to help circumvent state surveillance and censorship.

In Iran, demand for VPNs that allows users to mask their identity and access blocked sites, has surged more than 1,000?ily on average since protests began, according to research site Top10VPN.

Iranians are also using Nahoft - or "Hidden" in Farsi.

The Android encryption app turns Farsi text into a jumble of random words or a picture that can be sent as an attachment on a messaging app, said Mahmoudi of United for Iran, which helped build the app.

The Android encryption app turns Farsi text into a jumble of random words or a picture that can be sent as an attachment on a messaging app, said Mahmoudi of United for Iran, which helped build the app.

Since the protests began, 3 million to 4 million people in Iran have logged on every day to Psiphon, which allows users to set up a private server to access the internet and monitor banned sites such as Facebook and YouTube.

"It is important to tell people about safe tools to connect to the internet rather than tools that might be used against them, or for surveillance," said Psiphon's media manager Ali Tehrani.

REAL HARM
Iranian officials have said that facial recognition technology would be used to identify and punish any women who failed to wear a hijab, as publicly decreed.

Authorities have also created channels that encourage citizens to snitch on protesters, on platforms such as Telegram, Twitter and Instagram.

"Real harm is being done," said Nima Fatemi, founding director of nonprofit tech firm Kandoo

Authorities are also monitoring citizens through cellphone location tracking, said Amin Sabeti, founder of CERTFA, a cybersecurity firm.

"People have learned to turn off their mobile phones while going to protests because it is easy for the mobile company to find their exact location," he said.

Even ride-hailing or delivery apps are used to tell on women not wearing hijab correctly, with agents able to access data from private firms that offer no data protection, said Roya Pakzad, founder of advocacy group Taraaz.

"The government has always been keen to segregate women, control their public participation and limit their presence in public places, and they can use even these well-meaning or benign technologies to do it" she said.

"There are no checks and balances, no limit to how technology is used."

The Intercept - a news publication based in New York - said Iranian authorities use a software programme to alter, disrupt and monitor how customers use their phones, aiming to rupture encryption and track user movements.
A more tech-savvy government is a grave threat for Iranians, said Tahmasebi.

"This generation, as brave as they are, as invincible as they feel to be, face great risks," she said.

A more tech-savvy government is a grave threat for Iranians, said Tahmasebi.

"This generation, as brave as they are, as invincible as they feel to be, face great risks," she said.

"Because they are not aware of the ways the security forces are building cases against them by using surveillance and monitoring tools."