When Attackers Bypass the Banking Application: The Rise of Direct Payment-API Fraud

Financial cybercrime is entering a more dangerous phase.

For years, much of the public discussion around digital financial fraud has focused on phishing links, stolen passwords, account takeover, malicious mobile applications and social-engineering scams.

Those threats remain important. But a recent warning from India’s Computer Emergency Response Team (CERT-In) and CSIRT-Fin highlights something considerably deeper: attackers are targeting the infrastructure behind financial applications and directly invoking the APIs responsible for moving money.

On 9 October 2026, CERT-In/CSIRT-Fin reported multiple cyberattack campaigns affecting non-banking financial companies, digital-lending platforms, fintech companies, payment service providers and wallet operators. The attackers were observed compromising internet-facing applications, exposed APIs and privileged endpoints before stealing payment-gateway, aggregator or partner-bank API credentials.

The significance is not simply that credentials were stolen.

The attackers were able to use those credentials from infrastructure already trusted by the affected organizations and invoke disbursement or fund-transfer APIs directly.

That changes the security problem.

The financial application may no longer be the attacker's route to the money

A normal digital lending or payment transaction may involve several controls before funds can move.

A customer is identified. KYC checks are completed. A transaction or loan is created. A beneficiary is verified. Limits are checked. Approval may be required. Only then does the payment system initiate the transfer.

But what happens if an attacker reaches the infrastructure beneath that workflow?

CERT-In reported that attackers directly invoked fund-transfer and disbursement APIs while bypassing application-level checks including KYC, sanction processes, beneficiary verification, balance-sufficiency checks and transaction limits.

In other words, instead of defeating every security control individually, the attacker can attempt to reach the mechanism that ultimately tells the financial system:

Move the money.

That should concern banks, fintechs, payment companies and regulators far beyond the organizations directly observed in these incidents.

What the attacks looked like

According to CERT-In/CSIRT-Fin, initial compromise occurred through several familiar weaknesses: vulnerable internet-facing applications, deprecated or unauthenticated APIs, unrestricted upload functionality, long-lived API tokens embedded in source code, plaintext credentials and remote services without multi-factor authentication.

Once inside, attackers established persistence using web shells or backdoors, examined payment databases and API integrations, obtained payment or banking credentials and then initiated unauthorized transfers.

The observed fraudulent transactions included dummy transaction or loan reference identifiers, transactions exceeding normal limits and transfers to attacker-controlled mule accounts across multiple banks. CERT-In also observed rapid high-value transfers over IMPS and NEFT rails followed by immediate withdrawals.

The attack therefore crosses several traditional security boundaries.

It begins as a cybersecurity incident.

It becomes an identity and credential problem.

It reaches the payment infrastructure.

It then becomes financial fraud.

And once the attacker begins deleting logs or interfering with endpoint-security tools, it becomes a digital-forensics problem as well.

Anti-forensics makes the problem even more serious

One of the most important details in the advisory is the observation of log deletion or truncation, EDR tampering and other anti-forensic cleanup activity.

This matters because financial institutions often rely on logs to reconstruct what happened after suspicious transactions are identified.

If those records exist only on the compromised system, the same attacker who moves the money may also be capable of damaging the evidence needed to explain the transfer.

Financial-sector incident response therefore cannot depend solely on investigating the affected application after the event.

Evidence needs to exist across several independent layers: API gateways, identity systems, payment processors, bank integrations, network telemetry, endpoint monitoring and transaction records.

Centralized and tamper-resistant evidence becomes part of fraud prevention, not merely something investigators need afterwards.

Attack speed is also changing

CERT-In noted another important development: the interval between initial compromise and fraudulent fund transfer has become significantly shorter in recent incidents, with possible use of AI-assisted offensive tooling and large numbers of custom scripts.

That observation aligns with a broader trend.

Google Threat Intelligence Group reported in September that it had observed a financially motivated actor compromise cloud infrastructure and then plan, build and execute an agent-enabled mass credential-harvesting campaign in less than six hours. The agentic system automated vulnerability scanning, troubleshooting and credential harvesting with substantially less human intervention.

CERT-In followed on 15 October with a critical advisory describing incidents involving open-source agentic AI tools used for reconnaissance, exploitation and financially motivated intrusion. In one observed campaign, agentic tooling compressed the time from initial access to impact from days to only a few hours.

The implication for financial institutions is clear:

Fraud response designed around human-speed attacks may become too slow for machine-speed intrusion.

Why traditional fraud monitoring may miss this

Many fraud-control systems are optimized to identify suspicious customer behaviour.

Was the customer logging in from a new device?

Was an unusual beneficiary added?

Did the account suddenly transfer an abnormal amount?

Was authentication unusual?

Those controls remain necessary.

But direct API abuse introduces a different question:

What if the transaction did not originate from the customer journey at all?

A technically valid API request can still represent an illegitimate financial action.

An attacker using stolen credentials and trusted infrastructure may produce activity that appears valid at the network or authentication layer while being impossible according to the institution's actual business process.

This is why transaction monitoring needs to understand not only individual transactions but also transaction sequence and provenance.

A payout should not merely contain a valid reference number. The institution should be able to establish that the reference corresponds to a real approved process and that all required preceding stages actually occurred.

CERT-In specifically recommends cryptographically binding multi-stage transaction flows so that debit-stage APIs cannot be invoked unless required validation stages have already taken place. It also recommends maker-checker controls, beneficiary validation, real-time transaction monitoring, cumulative limits and near-real-time reconciliation with bank or aggregator statements.

APIs have become part of the financial attack surface

APIs are essential to modern financial services.

They connect banks, fintechs, wallets, payment gateways, lending platforms and external service providers. They enable speed, automation and interoperability.

But the same connectivity means API security can no longer be treated solely as an application-development concern.

A compromised payment API credential may effectively become a financial authorization instrument.

Organizations therefore need to know:

Which APIs can move funds?

Which credentials can invoke them?

Where are those credentials stored?

Which servers can call them?

Which APIs are obsolete but still reachable?

Can a payout endpoint operate independently of the normal customer or approval workflow?

And would security teams immediately detect such activity?

Those questions belong not only to software developers but also to CISOs, fraud teams, SOC analysts, digital-forensics investigators, risk managers and financial regulators.

From cybersecurity monitoring to forensic-aware financial defense

The emerging lesson is that financial cyber defense needs stronger integration between cybersecurity telemetry and financial transaction intelligence.

Security teams may see a web shell.

Fraud teams may see an abnormal transfer.

Identity teams may see unusual credential use.

A payment gateway may see technically valid API requests.

An investigator may later find deleted logs.

Viewed separately, each signal tells only part of the story.

Viewed together, they can reveal the complete attack chain.

This is where forensic-enriched threat intelligence becomes increasingly important.

Financial institutions need the ability to connect technical evidence—process activity, authentication events, API calls, network behaviour and endpoint telemetry—with the financial consequence: beneficiaries, transaction references, transfer values, timestamps and movement across institutions.

The objective should not simply be to detect malware.

It should be to establish evidence-to-action continuity from intrusion through transaction and response.

What organizations should do now

The CERT-In/CSIRT-Fin advisory provides extensive mitigation guidance, but several principles deserve immediate executive attention.

Payment and banking APIs should use strong authentication and short-lived credentials rather than long-lived static tokens. Deprecated and unused APIs should be removed, not merely forgotten. Sensitive credentials should be stored in appropriate secrets-management systems or hardware security modules. Administrative and payment infrastructure should use MFA, least privilege and controlled network exposure.

Organizations should also continuously reconcile financial transactions with the business records that supposedly authorized them. A transaction referencing a loan, payout or beneficiary that does not actually exist should never be accepted simply because the API call itself is technically valid.

Finally, organizations should preserve evidence independently of the systems an attacker may control. CERT-In recommends centralized logging with at least 180 days of retention and emphasizes forensic preservation following suspicious activity.

The bigger lesson

Digital financial fraud is no longer only about convincing a customer to click the wrong link.

Attackers increasingly understand the technology beneath digital finance.

They are looking for exposed APIs, forgotten endpoints, embedded credentials, weak cloud permissions and trusted servers capable of initiating financial actions.

The next major financial attack may therefore look completely legitimate to one part of the infrastructure while being completely impossible from a business perspective.

That is why the future of financial cyber defense must connect three disciplines that organizations have often managed separately:

Cybersecurity. Financial-fraud intelligence. Digital forensics.

When those disciplines operate together, an organization does not merely ask whether an API request was technically valid.

It asks the more important question:

Was this financial action legitimate, authorised and supported by verifiable evidence?

That distinction may become one of the defining security challenges of modern digital finance.

Sources and Further Reading

This article combines findings from recent official cybersecurity advisories and threat-intelligence research with analysis of their implications for financial institutions, fintech platforms, fraud-response teams and digital-forensics practitioners.

Primary Sources

1. CERT-In / CSIRT-Fin — CIAD-2026-0046
Threat Actors Exploiting Payment and Disbursement APIs for Unauthorized Fund Transfers in BFSI Entities — 9 October 2026
https://www.cert-in.org.in/s2cMainServlet?VLCODE=CIAD-2026-0046&pageid=PUBVLNOTES02

2. Google Threat Intelligence Group — GTIG AI Threat Tracker
From Prompting to Autonomy: The Evolution of Adversarial AI — 8 September 2026
https://cloud.google.com/blog/topics/threat-intelligence/from-prompting-to-autonomy-the-evolution-of-adversarial-ai

3. CERT-In — CIAD-2026-0049
Advisory addressing AI-assisted exploitation, accelerated attack operations, API security, forensic preservation and agent governance — October 2026
https://www.cert-in.org.in/s2cMainServlet?VLCODE=CIAD-2026-0049&pageid=PUBVLNOTES02

4. Google Threat Intelligence Group
Financially Motivated Threat Actor BREEZE COMET Targets Brazil — 1 September 2026
https://cloud.google.com/blog/topics/threat-intelligence/financially-motivated-threat-actor-breeze-comet-targets-brazil

Author’s Note

The documented incidents and technical observations referenced above are drawn from the cited official advisories and threat-intelligence research. Interpretations concerning forensic-enriched threat intelligence, transaction provenance, evidence-to-action continuity, and the convergence of cybersecurity, financial-fraud intelligence and digital forensics represent the author’s analysis of these emerging attack patterns.