As has become standard, Apple has quietly updated OS X definitions to counter a recently-publicized malware threat, checks show. Lion and Snow Leopard will now block a Trojan fronted by OSX/Revir.A, which in turn installs a backdoor program identified as OSX/Imuler.A. Although neither part of the Trojan is especially dangerous at the moment, Imuler could potentially be used at a later date to capture screenshots or steal files.