What Buyers Don’t Check – and

M&A cyber due diligence is one of the most critical – and most frequently underestimated – elements of any acquisition. Every M&A deal involves a careful examination of financials, legal exposure, and operational risk. Cyber security is almost always on the checklist. But being on a checklist and being properly assessed are very different things – and the gap between them is where deals unravel, valuations erode, and post-close surprises become expensive problems.

For buyers, the risk is straightforward: acquire a company without understanding its cyber posture and you may be inheriting a breach that hasn’t been disclosed, a regulatory exposure that hasn’t been assessed, or a technical debt that will take years and significant investment to resolve. For sellers, the risk runs in the other direction – poor cyber maturity can delay deals, invite price chips, or deter interest from sophisticated acquirers who know what to look for.

Getting cyber due diligence right is not about producing a report that satisfies a checklist. It’s about surfacing the issues that matter, understanding their implications for deal value, and having a clear plan for what happens after completion. That’s the difference between due diligence as a process and due diligence as a strategic advantage.

“Cyber risk doesn’t disappear at completion. It transfers – along with the liability, the remediation cost, and the reputational exposure that comes with it.”

Why Cyber Is Different from Other Due Diligence

Financial due diligence has decades of established practice behind it. Audited accounts, standardised reporting, well-understood metrics. Cyber due diligence is still maturing as a discipline, and the absence of standardised disclosure means that what one organisation calls a ‘security incident’ another might never have logged at all.

This matters because cyber risk is asymmetric in ways that other forms of business risk are not. A target company could have strong financials, a solid management team, and a defensible market position – while simultaneously harbouring vulnerabilities that, once inherited, create regulatory exposure across multiple jurisdictions, customer notification obligations, or integration costs that fundamentally change the deal economics.

There are four failure modes that appear repeatedly in M&A transactions where cyber due diligence was either skipped or treated as a formality:

Cyber Risk Across the Deal Lifecycle

Effective cyber due diligence isn’t a single assessment at a single point in the deal timeline. The risks and priorities shift as a transaction progresses, and so should the approach. CurveTech structures its M&A cybersecurity support across three distinct phases, each with its own objectives and deliverables.

Before the Deal: Readiness & Cyber Due Diligence

Establish a clear baseline of the target’s security posture across key controls, vulnerabilities, incident readiness, and compliance status. Identify and prioritise material risks early – reducing surprises, deal friction, and valuation uncertainty. For sellers, this phase is equally valuable: understanding your own posture before an acquirer does is the difference between managing the narrative and reacting to it.

During the Deal: Transaction Security & Risk Control

As transactions progress, attention shifts to legal and commercial detail. At the same time, organisational change, expanded access rights, and third-party involvement increase cyber exposure significantly. Managing this window – maintaining control of data flows, access permissions, and sensitive communications throughout due diligence and negotiation – requires deliberate security oversight that most deal teams aren’t resourced to provide.

After the Deal: Post-Completion Integration

Integration is where inherited risk becomes operational risk. Network connections between two previously separate environments, merged identity and access systems, combined data estates, and unified security tooling all create exposure if not managed carefully. Post-completion security planning should begin before the deal closes, not after.

What a Proper Assessment Actually Covers

A meaningful cyber due diligence assessment goes well beyond asking a target to complete a security questionnaire and reviewing their ISO certificate. The following gives a sense of the areas that matter most, and the level of materiality that should determine how deeply each is examined.

The output isn’t a pass or fail – it’s a risk-tiered picture of what’s present, what it means for deal value, and what remediation looks like in terms of time and cost. That picture can inform negotiation, deal structure, price adjustment mechanisms, or the conditions attached to completion.

A Note for Sellers

The Integration Risk Nobody Plans For

The period between deal completion and full technical integration is consistently the highest-risk window in any M&A transaction and consistently the least resourced for cyber purposes. The deal team has moved on to the next opportunity. The integration team is focused on operational continuity. Security is assumed to be someone else’s problem.

The reality is that connecting two organisational environments, even temporarily and with the best intentions, creates attack surface that didn’t previously exist. Credentials inherited from the target. Network bridges that bypass existing controls. Privileged access granted during the deal process and never revoked. In the absence of deliberate, sequenced integration planning, these aren’t edge cases. They’re the norm.

• Conduct a post-completion cyber assessment before connecting any environments – treat the target as untrusted until validated
• Validate patching, backup integrity, and access controls independently before integration begins
• Remove all unnecessary or inherited privileged access granted during the deal process
• Run joint incident response exercises before integration, not after – test readiness before the environment is live
• Align policies, monitoring, and security tooling across both organisations before full network connectivity
• Establish clear cyber ownership on both sides from the moment heads of terms are signed

How CurveTech Supports M&A Transactions

CurveTech provides end-to-end cybersecurity support across the full M&A lifecycle, from initial readiness assessments and cyber due diligence through to secure post-deal integration. The service is designed for both sides of the transaction: buyers who need an honest, evidence-based picture of what they’re acquiring, and sellers who want to enter the market with a mature, well-documented security posture that withstands scrutiny.

Whether you are preparing for a transaction, evaluating an acquisition, or integrating a newly acquired entity, CurveTech brings the expertise to manage cyber risk with clarity and confidence – without slowing the deal down.

Getting the Timing Right

The most common mistake in M&A cyber due diligence isn’t what gets examined – it’s when. Cyber assessment is frequently commissioned late in the process, after commercial terms are largely agreed and deal momentum is established. At that point, findings create friction: unwelcome surprises that neither party has the time or inclination to address properly, leading to either price adjustment mechanisms that compensate financially without fixing the underlying issues, or issues being downplayed to keep the deal moving.

Commissioning cyber assessment early, at the same time as financial and legal due diligence, changes the dynamic entirely. Issues are surfaced when there is still time to understand them properly, negotiate around them if necessary, and plan remediation before completion rather than inheriting it afterwards. For private equity firms and sophisticated acquirers making multiple transactions, embedding cyber due diligence as a standard pre-signing workstream is increasingly becoming the norm.

The question for buyers isn’t whether cyber risk exists in a target. It always does. The question is whether you understand it well enough to price it correctly, structure the deal around it appropriately, and integrate the business without it becoming your problem before you’ve had the chance to fix it.

Preparing for a Transaction?

Sources

1. Forescout Technologies, The Role of Cybersecurity in M&A Diligence (2019). Survey of 2,700+ IT and business decision makers across seven countries.
2. UK Information Commissioner’s Office, Penalty Notice: Marriott International Inc (October 2020). ICO reference: COM0804139.
3. Forescout Technologies, ibid. – 73% of respondents said an undisclosed data breach would be an immediate deal-breaker in their M&A strategy.