Leaked credentials: What we do to keep you safe

Nov 19, 2024 by Serena de Pater

What are leaked credentials?

Leaked credentials refer to compromised usernames and passwords that are inadvertently or maliciously exposed to unauthorized individuals. These credentials are typically obtained through methods such as malware, phishing, or hacking. Once compromised, they are sold, traded, or exchanged on a large scale, making them readily available to cybercriminals.

The problem of leaked credentials is rapidly increasing. These compromised combinations allow cybercriminals to bypass advanced technical defenses. Leaked credentials can be compared to an envelope with an address on it, containing a key to the front door. Since many people reuse their username and password combinations across different accounts, this can lead to widespread breaches. Without multi-factor authentication (MFA) during login processes, a single leaked credential set may grant cybercriminals access to your home, business, or sensitive data.

Do we leak credentials?

No, of course not! Our mission is to make the digital world safer by reporting vulnerabilities we discover in digital systems to those who can address them. We do this by identifying new zero-day vulnerabilities, scanning for known CVEs, and, thanks to our extensive network and strong connections in the cybersecurity community, acting on tips from our peers when necessary. Occasionally, we receive tips about so-called leaked credentials. One example of such a case is DIVD-2020-00013, which involved a phishing campaign impersonating the videoconferencing platform Zoom.

Our first case of leaked credentials

DIVD-2020-00013

At the end of November 2021, cybercriminals engaged in a phishing campaign posing as Zoom. If a victim fell for this scam and entered their personal credentials, those credentials got compromised.

While investigating this phishing campaign, a partner organization discovered that the compromised usernames and passwords were stored in improperly secured directories, unintentionally exposing them to public access. This meant that not only the criminals but anyone could access the credentials. The leaked credentials were downloaded from the internet. After connecting and collaborating with our partners, our CSIRT received the Dutch part (386 accounts) of the harvested credentials, so that we could inform potential victims.

How do we get leaked credentials?

Leaked credentials come into our possession through trusted sources, such as tips from partners in the cybersecurity community, or as part of investigations into specific incidents. For example, in phishing campaigns, the infrastructure used by cybercriminals may inadvertently expose compromised credentials, allowing researchers to recover them.

What do we do with leaked credentials?

Our priority is to ensure the data is handled responsibly, minimizing harm while protecting individual privacy. When a breach involves a small number of accounts (fewer than two million), we directly inform affected individuals.

For larger breaches, we create two types of summaries:

Email Domain Summary – Lists main email domains (like “example.com”) and the count of unique email/password combinations for each.
URL Domain Summary – Lists main domains from URLs tied to passwords and the count of unique email addresses for each. Only if the breach data includes website addresses (URLs) tied to the passwords.

We share these summaries with relevant organizations like national CERTs, CSIRTs, or corporate security teams. These teams can identify affected domains and request specific data to inform victims.

To protect privacy, we never send plain-text passwords. All traffic is encrypted, and the passwords are masked before sending. For example, for passwords that contain 10 characters or more, we only send the first two and last two characters and replace all other characters with an asterisk. To address ethical concerns about sharing PII with governments from countries with poor human rights records, we will only provide data to government organizations in countries that score above 0.4 on the most recent Human Rights Index.

We strictly follow ethical and privacy guidelines to ensure that the sharing of leaked credentials is conducted safely. By encrypting all communications, masking sensitive data, and limiting access to trustworthy organizations, we protect victims’ information while enabling them to take action. If you want to read our Code of Ethics, click here.

We are also mindful of human rights concerns. When working with government entities, we ensure that only those in countries with strong human rights records receive access to sensitive data. If you want to read our Code of Conduct, click here.

Are leaked credentials a security vulnerability?

Yes, leaked credentials represent a significant cybersecurity vulnerability. Like unpatched software vulnerabilities (CVEs), leaked credentials can be exploited by criminals. These breaches often lead to unauthorized access, data theft, or other forms of cyberattacks.

As volunteers, we have taken it upon ourselves to inform victims of cybercrime—not only those with vulnerable systems but also those whose credentials have been leaked online. Would you like to read more about how we deal with leaked credentials? Please visit our CSIRT Page.

Cases involving leaked credentials

DIVD-2024-00022 - Millions of credentials scraped from Telegram

On June 4, 2024, an anonymous security researcher reached out to DIVD CSIRT for help with notifying victims. The researcher and their partners had infiltrated several Telegram chat groups where large volumes of account information were being exchanged. Our plan is to collaborate with CERTs, CSIRTs, and security teams, sharing the list with them so they can identify apex domains for which they need more detailed data. Read more here.

DIVD-2024-00019 - Victim Notification Operation Endgame

Operation Endgame is the largest anti-botnet operation to date, during which international law enforcement infiltrated major botnets like Smokeloader and IcedID, obtaining victim data—including email, ADFS, and account credentials—that was shared with cybersecurity organizations for mitigation and awareness efforts. Read more here.

DIVD-2021-00015 - Telegram OD

During an investigation into vendors who sell stolen credentials, one of our researchers discovered a Telegram group full of usernames and passwords that criminals had stolen from their victims’ systems or by hacking into companies, websites, and services. Since this was an open Telegram group, we were able to extract the stolen data to notify the victims. Read more here.

DIVD-2021-00012 - Warehouse Botnet

During an investigation into open database servers in the Netherlands, one of our researchers discovered a database belonging to criminals containing stolen usernames and passwords. Since the database was not secured, we were able to download all the stolen data so we could notify the victims. Read more here.

DIVD-2021-00004 - Leaked phishing credentials

In April, a security researcher reported to DIVD that a phishing campaign was underway, targeting various individuals and organizations using Active Directory Federation Services (ADFS). The researcher also reported that due to weak security in critical directories, the criminals’ servers were leaking the compromised data. DIVD CSIRT received the data from the researcher intending to notify the victims via email in the coming days. Read more here.

DIVD-2020-00013 - Leaked phishing credentials

In late November, criminals ran a phishing campaign using fake Zoom invitations and email quarantine messages. A researcher from a partner organization discovered that the phishing server leaked compromised email/password combinations due to weak security. DIVD CSIRT received the Dutch portion of these lists to notify the affected victims. Read more here.