Hur'q Signalling Device
A Hur'q Signalling Device is a piece of secret Dominion technology that emits a signal identical to that used by the Hur'q. The effective outcome of this is that any Hur'q who respond to the signal will converge on the device, destroying anything in their path.
Three of these devices were found by the Alliance - first one on Bajor (which prompted the attack in “Scylla and Charybdis”), second one on Karemma (which had seceded from the Dominion) and the third on an Ancient Dominion Station in the Masan System (which was most likely planted there by Female Changeling to prevent Odo's team from completing the survey of the station).
It is probable that devices were present on all other planets which have been attacked by the Hur'q as the devices are part of the Dominion's manipulation of the Hur'q into attacking their enemies and punishing those worlds who reject Dominion rule.