Marcus D. Ellison

Education

B.S. Computer Information Systems2012 - 2016

Texas A&M University – San Antonio, San Antonio, TX

Concentration in Network Security; Dean's List 2014–2016

Skills

SIEM Engineering (Splunk ES, IBM QRadar) · Endpoint Detection & Response (CrowdStrike Falcon) · Vulnerability Management (Tenable.io, Qualys) · Penetration Testing (Burp Suite, Metasploit) · Incident Response & Digital Forensics · PCI-DSS / HIPAA / SOC 2 Type II Compliance · MITRE ATT&CK Framework · Certified Information Systems Security Professional (CISSP) · CompTIA Security+ CE

Links

LinkedIn: linkedin.com/in/marcusellison-infosec · GitHub: github.com/mellison-sec · Certification: CISSP #748291 (verifiable via ISC2)

Profile

Senior Information Security Analyst with 8 years of experience in threat detection, incident response, and vulnerability management across financial services and SaaS environments. Specializes in SIEM engineering, zero-trust architecture, and regulatory compliance (PCI-DSS, SOC 2 Type II). Reduced mean time to detect (MTTD) by 41% at current employer by rebuilding detection rule logic across a 12,000-endpoint estate.

Work Experience

Senior Information Security AnalystMar 2021 - Present

Crestline Financial Technologies, Austin, TX

Redesigned 200+ SIEM correlation rules in Splunk ES, cutting false-positive alert volume by 34% and freeing 18 analyst-hours per week for high-priority investigations.
Led a 14-person cross-functional incident response to a supply-chain intrusion, containing the breach within 6 hours and preventing estimated $2.4M in potential data-exfiltration losses.
Built an automated vulnerability triage pipeline using Tenable.io and Jira APIs, reducing average patch SLA from 21 days to 9 days across 430 cloud and on-prem assets.

Information Security Analyst IIJun 2018 - Feb 2021

Vantara Health Systems, Dallas, TX

Deployed CrowdStrike Falcon across 6,800 endpoints in 11 weeks, achieving 99.3% coverage and eliminating a legacy AV tool that carried $180K in annual licensing cost.
Conducted quarterly penetration tests on patient-portal web applications using Burp Suite and Metasploit, identifying and remediating 27 critical findings before two successive HIPAA audits with zero findings.
Authored the organization's first Threat Intelligence Program, ingesting 4 commercial and 6 open-source feeds into a MISP instance and producing bi-weekly executive briefings adopted by the CISO.

Junior Information Security AnalystAug 2016 - May 2018

Holloway Managed Security Services, San Antonio, TX

Monitored and triaged 300–500 daily alerts across 23 client environments using IBM QRadar, maintaining a 98.7% SLA adherence rate over 22 consecutive months.
Performed monthly vulnerability scans with Qualys and delivered prioritized remediation reports, helping three clients achieve PCI-DSS compliance within 90-day deadlines.
Developed an internal runbook library of 40 playbooks for common threat scenarios, cutting new-analyst onboarding time from 6 weeks to 3.5 weeks.