The locator bomb was a weapon of Ferengi manufacture, primarily designed for assassinations.
The device contained a sorium-argine explosive and homed in on a specific target individual's pheromones. Once locked on, the bomb was very accurate and difficult to avoid.
Krax and Rom used a locator bomb in a failed attempt to assassinate Quark when he briefly became Grand Nagus in 2369. (DS9: "The Nagus")