Internet giant Google says malicious software has been used to spy on tens of thousands of Vietnamese web users.
The company said the cyber attacks appeared to target opponents of bauxite mining in Vietnam.
Google said the malware was "damaging" but less sophisticated than recent attacks at the heart of the company's dispute with China.
But computer security firm McAfee suggested the perpetrators could be connected to Vietnam's government.
Writing on his blog, Neel Mehta of Google's security team said the malware had "infected the computers of potentially tens of thousands of users" around the world.
It installed itself when users downloaded the software needed to type Vietnamese characters, he said.
The infected computers were then used to spy on the users or to block other sites "containing messages of political dissent".
"Specifically, these attacks have tried to squelch opposition to bauxite mining efforts in Vietnam, an important and emotionally charged issue in the country," said Mr Mehta.
The mine operations have attracted criticism in Vietnam over concerns about environmental damage.
George Kurtz, Chief Technology Officer and Executive Vice President of McAfee, which has been working with Google to uncover the hacking, said the action appeared to be "a politically motivated attack", because of the individuals and organisations affected.
"We believe that the perpetrators may have political motivations and may have some allegiance to the government of the Socialist Republic of Vietnam," said Mr Kurtz.
The Vietnamese government has not responded to the allegations.
The alleged cyber attacks come amid an ongoing row between China and Google about the censoring of online content.
Google said it would stop censoring its search results after it complained of a "sophisticated cyber attack originating from China" targeting the email accounts of human rights campaigners.
