Google Inc. accused Vietnam on Wednesday of stifling political dissent with cyberattacks, the latest complaint by the Internet giant against a communist regime following a public dispute with China over online censorship.
Like China, Vietnam tightly controls the flow of information and has said it reserves the right to take "appropriate action" against Web sites it deems harmful to national security.
The cyberattacks targeted "potentially tens of thousands," a posting on Google's online security blog said.
It said it was drawing attention to the Vietnam attacks because they underscored the need for the international community "to take cybersecurity seriously to help keep free opinion flowing."
Google apparently stumbled onto a scheme targeting Vietnamese-speaking Internet users around the world while investigating the surveillance of e-mail accounts belonging to Chinese human rights activists, one analyst suggested.
The attackers appear to have targeted specific Web sites and duped users into downloading malware programs, said Nart Villeneuve from The Citizen Lab at the University of Toronto. That may have allowed the infiltration and surveillance of activists, he said.
"This kind of stuff happens all the time in China," said Villeneuve. "It has a chilling effect. It silences people."
Google engineer Neel Mehta wrote in the posting, "these attacks have tried to squelch opposition to bauxite mining efforts in Vietnam, an important and emotionally charged issue in the country."
The mining project involving a subsidiary of Chinese state-run aluminum company Chinalco is planned for Vietnam's Central Highlands and has attracted strong opposition.
Foes fear the mine would cause major environmental problems and lead to Chinese workers flooding into the strategically sensitive region.
The computer security firm McAfee, which has investigated the malware, also discussed the attacks in a blog posting Tuesday.
"We believe that the perpetrators may have political motivations and may have some allegiance to the government of the Socialist Republic of Vietnam," wrote George Kurtz, McAfee's chief technology officer.
Vietnamese officials did not respond to requests for comment Wednesday.
Last fall, the government detained several bloggers who criticized the bauxite mine, and in December, a Web site called bauxitevietnam.info, which had drawn millions of visitors opposed to the mine, was hacked.
The malware apparently began circulating at about that time, according the McAfee blog. It said someone hacked into a Web site run by the California-based Vietnamese Professionals Society and replaced a keyboard program that can be downloaded from that site with a malicious program.
Google says its dispute with China was triggered by a hacking attack that emanated from the mainland and attempts to snoop on dissidents' e-mail.
Last week, Google shut down its search operations in China, Vietnam's northern neighbor, after complaints of cyberattacks and censorship there. Google now redirects search queries from China's mainland to the freer Chinese territory of Hong Kong.
On Tuesday, many users of the Chinese Google search engine experienced difficulties. Analysts suggested the troubles may be linked to the company's decision to move to Hong Kong.
Google initially said it was an in-house technical problem but later shifted its explanation, blaming the "Great Firewall" — the nickname for the network of filters that keep mainland China's Web surfers from accessing material the government deems sensitive.
The sudden disruption and lack of explanation fit with how the government has brought companies to heel previously in the heavily monitored Chinese Internet industry, analysts said.
"I don't think anyone should be surprised," said Bill Bishop, a Beijing Internet entrepreneur and author of the technology blog Digicha. Tuesday's problems were payback by the government, he said, because "Google humiliated China."