A suicide bomb and gun attack on a government security office in central Kabul has killed at least 28 people and wounded over 300.Most of the victims were civilians, including women and children, with the Taliban having claimed responsibility for the attack.This is the worst single militant strike in Kabul since 2011, when about 60 people died in a suicide blast outside a mosque.So, what does the latest deadly attack tell us about the Taliban's current strength?How should we evaluate the overall security situation across Afghanistan? And where does the country's future lie when faced with the gradual withdrawal of foreign troops?