At least 24 Afghan soldiers were reported killed in their sleep on Friday when a group of infiltrating Afghan police carried out an insider attack on a joint police and army headquarters in Qalat. The attack was at three in the morning, while everyone was asleep.
The Zabul Province, and Qalat in particular, are Taliban-heavy regions, and insider attacks like this are a classic Taliban tactic. It is thus assumed the Taliban are likely behind the attack, though they have yet to confirm this.
In the past, infiltration was trivially easy, because the Afghan government is always desperate for recruits. Some infiltration is done just to get free training and to leave with a gun. Other times, infiltrators assigned to smaller checkpoints kill everyone else overnight, loot everything they can carry and join the Taliban. This is how the Taliban gets a lot of its weaponry and ammunition.
Since the US-Taliban peace deal, the Taliban has conducted fewer major attacks against Afghan government targets, though they have continued to attack some since the government has refused to fulfill promised prisoner releases.