Attack on Burger King underlines problems for a fast-growing advertising venue

While most Americans were winding up their holiday weekends last Monday, the phones at the Vancouver, British Columbia, headquarters of HootSuite, a social media management company, began to ring.

Burger King’s Twitter account had been hacked. Its logo had been replaced by a McDonald’s logo, and rogue announcements began to appear. One was that Burger King had been sold to a competitor; other posts are unprintable.

“Every time this happens, our sales phone lines light up,’’ said Ryan­ Holmes, chief executive of HootSuite, which provides management and security tools for Twitter accounts, including the ability to prevent someone from accessing an account. ‘‘For big brands, this is a huge liability,’’ he said, referring to the potential for being hacked.