Japanese firm Trend Micro chose Octopus Communications after a four-way pitch. It replaces incumbent NSPR, which had held the account for three years.
The new brief will focus on positioning Trend Micro as the security choice for family protection, as the option for small businesses and as a leader in the security market for large enterprise customers.
Jon Lonsdale, MD of Octopus, said the agency would be handling both the consumer and b2b sides of the firm's PR.
He said: 'We want to ensure Trend Micro is the leader in highlighting issues affecting the consumer and for internet usage, as well as being the main port of call for business customers.'
Octopus will also work to boost Trend Micro's social media profile.
The search for a new agency follows changes to the firm's PR across the EMEA region during 2010.
Trend Micro manufactures security software including brands such as Titanium, which can be downloaded to protect computers from viruses.
Founded in 1988, the Tokyo-based firm has more than 4,000 staff and operations in more than 30 countries.
Octopus' other internet clients include Mimecast, which employed the agency to position it as an email security specialist.