Research In Motion, the maker of the BlackBerry smartphone struggling to revive falling sales, rose 4.5 percent on speculation that activist investor Carl Icahn is buying a stake in the company.

“This is a typical Carl Icahn scenario to come in and change,” said Sameet Kanade, an analyst at Northern Securities Inc. in Toronto who recommends investors sell the stock. “If he did this though, it would have to be on a hostile basis, given that the two co-CEOs own 11 percent of the stock.”

RIM has plunged 61 percent on the Nasdaq Stock Market this year after earnings missed analysts’ estimates on slumping demand.