The attack targeted a previously unknown vulnerability on Microsoft’s Internet Explorer 8. Cisco security pros say the attackers appeared to have two motives: Infiltrate government networks and gather information from the computers compromised initially in order to prepare for future attacks. The attack on the Labor Department site was also highly targeted. Experts believe the attack targeted government employees involved in developing nuclear weapons. The attackers’ malware only worked on IE8 running on Windows XP computers, an indication that they knew their targets used those types of systems.”]
Source: https://www.csoonline.com/article/2133405/labor-department-hackers-more-sophisticated-than-most.html