Account takeover didn’t disappear — it evolved

Account takeover (ATO) and credential abuse aren’t new.
What’s changed is how attackers do it and why many traditional defenses no longer catch it early.

Today’s ATO attacks don’t always start with:

• brute force login attempts
• obvious credential stuffing spikes
• suspicious IP addresses

Instead, they increasingly rely on:

• session hijacking
• MFA fatigue or bypass
• reused credentials tied to real identities
• low-and-slow abuse that blends in

The result: fewer alerts, more successful takeovers.

This shift reflects a broader trend Constella has highlighted: identity risk has become the front door to modern breaches, replacing many traditional perimeter-based entry points.

The modern ATO playbook (what attackers do now)

1) Session hijacking replaces password guessing

Infostealer malware has fundamentally changed the ATO landscape.

Instead of stealing only usernames and passwords, attackers now harvest:

• Active session cookies
• Authentication tokens
• Browser fingerprints
• Device context

With a valid session, attackers can:

• Bypass login screens entirely
• Avoid MFA challenges
• Inherit “trusted device” status

From a detection standpoint, this often appears to be a legitimate user continuing an existing session.

These tactics frequently surface first in dark web and underground ecosystem monitoring, where stolen sessions and identity artifacts are traded at scale.

2) MFA isn’t broken — but it’s no longer enough

MFA still plays an important role.
But attackers increasingly work around it instead of trying to defeat it directly.

Common techniques include:

• MFA push fatigue
• Phishing frameworks that proxy MFA in real time
• Token replay
• Abuse of remembered devices
• Session takeover after MFA has already been completed

The takeaway is simple but critical:
Passing MFA does not mean the session is safe.

This is why ATO detection can’t rely solely on authentication events. It must incorporate broader exposure to identity and behavioral context.

3) Credential reuse fuels scale

Even as attack techniques evolve, credentials still matter — just not in isolation.

Attackers increasingly rely on:

• Previously exposed credentials
• Password reuse across personal and corporate accounts
• Breached emails tied to real individuals
• Identity fragments collected over time

Constella’s 2025 Identity Breach Report highlights just how widespread identity exposure and reuse have become, creating a massive attack surface for ATO and fraud.

The goal for attackers isn’t speed.
It’s persistence, blending in long enough to extract value.

Why does ATO detection fail more often now

Many defenses are still designed around login events.

But modern ATO activity increasingly happens:

• After authentication
• Inside valid sessions
• Using real identities
• With minimal anomalies

This creates blind spots when teams rely on:

• login-only monitoring
• IP reputation alone
• single-signal alerts
• identity verification without exposure context

Identity verification can confirm legitimacy in the moment — but it doesn’t explain ongoing identity risk.

What signals actually matter for preventing credential abuse

Detecting ATO earlier requires shifting from a login-centric approach to identity risk and session context.

Identity exposure signals

• Known breach exposure tied to a user
• Credential reuse across services
• Presence in infostealer logs
• Identity clusters linked to prior abuse

Session behavior signals

• Session token reuse from new environments
• Device fingerprint drift mid-session
• Impossible session continuity
• Privilege escalation after idle periods

Correlation signals

• Exposure combined with unusual session behavior
• Identity reuse across multiple accounts
• Repeated access patterns tied to the same identity cluster

These are the types of signals that identity intelligence and investigations teams rely on to reduce noise and surface meaningful risk.

Reducing false positives while improving detection

One of the biggest challenges in ATO defense is alert fatigue.

The solution isn’t more alerts — it’s better prioritization.

Teams that reduce false positives focus on:

• scoring identity risk before suspicious behavior
• correlating exposure with session activity
• prioritizing users with known reuse patterns
• grouping alerts by identity clusters rather than individual accounts

This identity-first approach enables:

• faster investigations
• earlier intervention
• fewer unnecessary escalations
• less customer friction

What the 2026 ATO landscape looks like

Looking ahead, expect:

• Continued growth in session-based abuse
• Broader infostealer-driven exposure
• More creative MFA bypass techniques
• Increased targeting of “trusted” users
• Fewer obvious fraud indicators

Organizations that adapt will treat identity exposure as an early warning system, not just a post-incident artifact.

Takeaway

Account takeover hasn’t gone away — it’s become quieter, more patient, and more identity-driven.

Defending against modern ATO requires:

• Understanding identity exposure
• Correlating session and behavior signals
• Prioritizing identity risk, not just alerts

As attackers evolve their playbook, detection strategies must evolve with them.