Dan Mackin


Dan Mackin is Co-CEO at Rule4. Dan is well-known in the industry for applying opensource and cybersecurity technology at enterprise scale. Prior to Rule4, Dan spent 12 years at AppliedTrust, where he was the COO before transitioning to Senior Vice President of Professional Services upon the company’s acquisition by a nationwide datacenter operator. In those roles, he funneled his high energy into a wide variety of client projects, as well as management of the company’s day-to-day operations. On the technical side, Dan led client engagements involving large-scale Linux server environments. He also led compliance efforts involving standards such as the Payment Card Industry Data Security Standard (PCI DSS), the Health Insurance Portability and Accountability Act (HIPAA), and the Federal Information Security Management Act (FISMA).

Dan holds a B.S. in electrical and computer engineering (ECE) from the University of Colorado at Boulder, and he is a coauthor of the Unix and Linux System Administration Handbook, currently in its fifth edition. As part of his commitment to the Colorado IT community, Dan curates the Boulder Linux Users Group (BLUG) meetup, which is held monthly at the Rule4 office in Boulder. He also firmly believes in the importance and power of volunteerism in the community at large, and he volunteers at and serves on the board for the Sister Carmen Community Center.

Away from the office, Dan likes to sink his teeth into new creative pursuits, whether it’s welding, woodworking, or applying Linux and other opensource technologies to automation, monitoring, and metrics collection projects. He loves cheering on the Colorado Buffaloes and Dallas Cowboys, skiing, camping, sailing, backcountry touring, four-wheeling, and spending time with his wife and dog.

Follow him on Twitter @dan_mackin or Instagram @squirrelmack.


  • Certified Information Systems Security Professional (CISSP)
  • GIAC Systems and Network Auditor (GSNA)
  • Payment Card Industry Qualified Security Assessor (PCI QSA)
  • Red Hat Certified System Administrator (RHCSA)