Security firm Flashpoint published an interesting paper titled, Cybercrime Economy: An Analysis of Cybercriminal Communication Strategies about cybercriminal communications of threat actors. Cybercriminal Communications use a variety of software alongside with the access to communities in the deep and dark web. This is done in order to carry out cross domain organization for crimes like phishing, credit card fraud, spam, and every sort of attack that pass through the corporations filters and defenses. The most used programs by cybercriminals are ICQ, Skype, Jaber, Pretty Good Privacy, Pidgin, PSI and AOL Instant Messenger (AIM)”]
Source: http://securityaffairs.co/wordpress/58194/cyber-crime/anatomy-cybercriminal-communications.html