Adversary simulation is a higher-tier, threat-led form of offensive security testing. Engagements are longer than typical red teams, usually 4 to 12 weeks of active testing, and built around assumed-breach scenarios, custom tooling, and the goal of mimicking a specific real-world threat actor mapped to MITRE ATT&CK. Financial regulators are the primary source of demand: TIBER-EU under DORA in the EU, CBEST under the Bank of England, and parallel national frameworks like TIBER-DE and TIBER-NL drive most of the spend at this tier. The engagement model differs from a generalist red team in that it is goal-oriented, slow-paced by design, and informed throughout by bespoke threat intelligence.
When choosing an adversary simulation provider, look for CBEST or TIBER-EU eligibility (these schemes pre-vet a small number of providers), evidence of custom offensive tool development, demonstrated EDR-evasion experience, attribution restraint and clean operational tradecraft, and a methodology rigorous enough to satisfy a regulator's threat-led test plan. The shortlist below filters the directory down to providers with documented experience in this category.
Related: Threat-led penetration testing (TLPT) · DORA TIBER-EU testing · STAR methodology providers
UK offensive security consultancy delivering CREST-accredited penetration testing, adversary simulation and CBEST, TIBER-EU and TBEST threat-led testing, mainly for financial services and other large organisations.
Global enterprise cybersecurity consultancy founded in 1999 in Oxford, holding rare CREST STAR-FS accreditation and delivering penetration testing, red and purple teaming, and PCI QSA services across five international offices.
Global Big Four professional services firm delivering CREST, CHECK, and CBEST-accredited penetration testing and red teaming services from London, serving the UK's largest enterprises and regulated organisations.
Elite UK offensive security consultancy specialising in CBEST/STAR/TIBER red teaming, advanced adversary simulation, and CREST-accredited penetration testing for FTSE 100 clients.
Full-service London-based cybersecurity consultancy with CREST, CHECK, and NCSC accreditations delivering offensive testing, managed detection, and strategic advisory services.
US penetration testing firm founded in 2011, running 600+ engagements a year with a fully remote, US-based team. Manual, expert-led testing across web, network, cloud, mobile, wireless, OT/ICS, and AI/LLM. Gartner Sample Vendor for PTaaS.
CREST and CHECK-accredited UK penetration testing consultancy with CBEST approval, specialising in infrastructure, application, and simulated attack assessments across the public and private sectors.
CHECK and CREST-accredited Birmingham-based cyber security consultancy with over 15 years of experience delivering penetration testing, red teaming, and OT security assessments for government and private sector clients.
World-renowned cybersecurity firm now part of Google Cloud, delivering threat intelligence-led penetration testing and red teaming informed by front-line incident response experience.
Award-winning Cheltenham-based cybersecurity consultancy with NCSC CHECK Green Light status and CREST approval, specialising in defence, government, and critical national infrastructure security.
Offensive security firm founded by former NSA operator David Kennedy, delivering CREST-accredited penetration testing, red teaming, and adversary simulation to Fortune 500 and government clients.
Cybersecurity division of the Thales Group, with ANSSI, CREST, FedRAMP 3PAO, and NATO-cleared personnel. Defence, government, and critical infrastructure penetration testing worldwide.
Helsinki-headquartered Finnish cybersecurity firm with roots dating to 1988, offering CREST-accredited penetration testing and deep expertise in EU regulatory compliance including GDPR, NIS 2, and TIBER-EU.
Adversary simulation is a threat-led form of offensive security testing in which a tester emulates the tools, techniques, and procedures (TTPs) of a specific real-world threat actor to test an organisation's detection and response capabilities end-to-end. Engagements are goal-oriented (e.g. reach a defined crown-jewel asset), use assumed-breach scenarios, and are mapped to frameworks like MITRE ATT&CK.
Red teaming is the broader category, any objective-driven, end-to-end attack simulation. Adversary simulation is a more specific tier within it: longer engagements, driven by bespoke threat intelligence about a named actor, deliberately slow-paced to test detection over time, and usually required by financial regulators rather than chosen voluntarily. A typical commercial red team is faster and less prescriptive about which actor is being emulated.
TIBER-EU (Threat Intelligence-Based Ethical Red Teaming for the European Union) is the European Central Bank's framework for intelligence-led red teaming of significant financial entities. National variants, TIBER-DE in Germany, TIBER-NL in the Netherlands, and others, implement the same model. Under DORA, threat-led penetration testing aligned to TIBER-EU is mandatory for many large financial institutions across the EU.
Adversary simulation engagements typically run 4 to 12 weeks of active testing, with an additional 2 to 4 weeks of threat intelligence and scoping work upfront and 2 to 4 weeks of reporting and purple-team replay afterwards. The full programme, including regulator engagement under TIBER-EU or CBEST, often spans 6 to 9 months end-to-end.