HANOI, Vietnam (AP) -- Working on her blog in California one day, Vietnamese democracy activist Ngoc Thu sensed something was wrong. It took a moment for a keystroke to register. Cut-and-paste wasn't working. She had "a feeling that somebody was there" inside her computer. Her hunch turned out to be right.
A few days later, her personal emails and photos were displayed on the blog, along with defamatory messages. She couldn't delete them; she was blocked out of her own site for several days as her attackers kept posting private details.
"They hurt me and my family. They humiliated us, so that we don't do the blog anymore," said Thu, who is a U.S citizen. She has resumed blogging, but now the Vietnamese government is blocking her posts.
Activists and analysts strongly suspect Hanoi was involved in that attack and scores of others like it.
They say a shadowy, pro-government cyber army is blocking, hacking and spying on Vietnamese activists around the world to hamper the country's pro-democracy movement.
IT experts who investigated last year's attack on Thu said the hackers secretly took control of her system after she clicked on a malicious link sent to her in an email. By installing key-logging software, the hackers were able to harvest passwords, gaining access to her private accounts.
Subsequent investigation also found that an upgraded version of the malicious software, sent by the same group, was emailed to at least three other people: a British reporter for the Associated Press reporter based in Hanoi; a France-based Vietnamese math professor and democracy activist; and an American member of the Electronic Frontier Foundation, an online activist group, living in the United States. None of the three clicked the link.
It appears to be the first documented case of non-Vietnamese being attacked by a pro-government hacking squad that had already conducted attacks well beyond the borders of this Southeast Asian nation. Its actions would appear to violate the law in the United States at least.
"You see campaigns being waged against Vietnamese voices of dissent in geographically disparate regions. Now we have seen an escalation against people who report on those voices," said Morgan Marquis-Boire, a University of Toronto researcher and online privacy activist who dissected the malware and published the findings with the EFF. "It's unlikely that this is the work of an opportunist individual."
Suspicion of state involvement is based in part on the fact that attackers have spent tens of thousands of dollars hiring servers around the world from which to launch attacks, often changing them after a few days. This is because the attackers know activists will ask service providers to take them down, said Dieu Hoang, an Australian computer engineer who, along with several other activists, works to help defend the Vietnamese activists online.
Attempts to monitor and harass dissidents online mirror the government's efforts to suppress them on the ground, where activists report persistent and occasionally violent harassment by state agents. The state convicted at least 63 bloggers and other nonviolent democracy activists in 2013 of criminal offenses, according to Human Rights Watch.
Vietnam is by no means unique in seeking to spy on electronic communications, as recent revelations about the actions of the National Security Agency in the United States demonstrate. But its activities are of special concern because of its human rights record in general.
Asked to comment on suspicions of state involvement in targeted surveillance, as well as the attack on the AP reporter, the Vietnamese government gave this brief statement: "Vietnam shares the attention of other countries in ensuring Internet security and is willing to cooperate with other countries in fighting high-tech crimes in general and Internet crimes in particular."
Suppressing online dissent in Vietnam is becoming more difficult because of soaring Internet usage. Close to 40 percent of the country's 90 million people have Internet access, and because Vietnam has been less effective than China in restricting that access, many people are viewing uncensored news. Dissidents can network and publicize their activities -- and acts of state repression -- with comparative ease.
Security researchers have found hints of how Hanoi may be dealing with the challenge.
In 2010, Google and McAfee alleged that that malicious software had been used to spy on tens of thousands of Vietnamese web users. McAfee said the perpetrators of the attacks "may have some allegiance" to the country's government. Last year, researchers led by Marquis-Boire, who also works for Google as a security engineer, uncovered evidence suggesting a spyware suite called FinFisher was being used to track activists' mobile communications inside Vietnam.