The payment ecosystem has become a prime target for cybercriminals. Despite the implementation of robust security protocols like EMV® 3-D Secure (3DS), attackers continue to exploit vulnerabilities, threatening the integrity of online transactions. Two of the most pressing threats facing issuers and Access Control Servers (ACS) today are Distributed Denial of Service (DDoS) attacks and Bank Identification Number (BIN) attacks.
The Growing Threat of DDoS Attacks
A DDoS attack occurs when malicious actors flood an online service, such as a website, API, or ACS (Access Control Server), with overwhelming traffic, rendering it slow or completely inaccessible. These attacks are not only increasing in frequency but also in sophistication. In fact, DDoS attacks surged by 55% from 2023 to 2024, driven by a wide range of threat actors including hacktivists, financially motivated criminals, and even nation-state actors.
The consequences of a successful DDoS attack are severe:
- Business disruption and downtime
- Loss of revenue (estimated at $6,130 per minute)
- Reputational damage
- Regulatory penalties
Understanding 3DS, ACS, and BIN attacks
3DS is a globally adopted authentication protocol developed by EMVCo to secure card-not-present (CNP) transactions. At the heart of this protocol is the ACS, used by banks to verify the identity of cardholders using data points like device IP, location, and behavioral patterns. However, bad actors are exploiting vulnerabilities in this process by conducting BIN attacks. BIN attacks are a form of card testing where fraudsters use automated scripts to guess valid card details. Here’s how they exploit ACS vulnerabilities:
- A DDoS attack is launched to crash the issuer’s ACS.
- Mastercard’s stand-in service authenticates transactions in the ACS’s absence.
- Fraudsters exploit this window to test stolen card numbers and execute fraudulent transactions.
Building Robust ACS Protection
As cyber threats continue to evolve, so must our defenses. DDoS and BIN attacks are not just technical nuisances, they are strategic threats to the trust and stability of the digital payment ecosystem. This is where Mastercard’s Threat Protection steps in. With Threat Protection, issuers and ACS providers can ensure the availability, integrity, and security of their authentication systems, keeping fraudsters at bay and customers protected. Our cloud-based, always-on solution is designed to safeguard Internet-facing assets, including ACS platforms.
Here is how it works:
- Redirect: Traffic is routed through Mastercard’s Threat Protection Centers via a simple DNS change.
- Clean: Malicious traffic is filtered out at both network and application layers.
- Receive: Only clean, legitimate traffic reaches the ACS, ensuring uninterrupted service.
With always-on Layer 4 DDoS mitigation, Threat Protection ensures that ACS platforms remain available and responsive even during high-volume attacks so issuers can maintain control over authentication decisions and minimize reliance on stand-in services.
Enhanced Protection with IP Intelligence
A key differentiator is Threat Protection's IP Intelligence. Beyond Layer 4 mitigation, Threat Protection leverages rich IP intelligence to proactively block malicious actors based on previous behaviors and traffic patterns. Our Threat Protection module automatically integrates this intelligence to preemptively block high-risk traffic.
ACS service providers can also benefit from subscribing to our IP intelligence feed for an additional layer of security. With this module, ACS can identify malicious IP addresses in the authentication request, enabling them to make more informed authentication decisions and increase the accuracy of risk-based assessments. This, in turn, reduces the likelihood of fraud for which issuers are liable and decreases their exposure to financial loss.
Securing ACS Availability and Integrity
The availability and integrity of Access Control Servers are non-negotiable for issuers, cardholders, and the overall payments ecosystem. DDoS and BIN attacks not only threaten downtime but they open the door to fraud, increase issuer liability, and erode trust in the authentication process. Mastercard’s Threat Protection helps protect ACS platforms from these threats, ensuring that authentication decisions remain in the hands of issuers, not fraudsters.
By combining real-time DDoS mitigation, intelligent traffic filtering, and global threat insights, Threat Protection empowers ACS providers to deliver secure, uninterrupted authentication services. In doing so, it strengthens the entire 3DS ecosystem—protecting issuers, merchants, and cardholders alike.
