What is a Data Leak?

Understand what data leaks are, the difference between data leaks and breaches, their causes, and discover effective prevention strategies to safeguard your sensitive information.

Your enterprise collaboration platforms could be an open door for data exfiltration.

What if we told you there was a place where confidential information is available to almost your entire organization? Where outsiders are invited in and data can be accessed, downloaded, or copied in a click. Unless you’ve taken steps to prevent it, it’s happening in your organization right now.

We’re talking about enterprise collaboration and social network tools. Most companies use at least two. Slack, Microsoft Teams, Workplace from Meta, Yammer…. All these platforms are helping to break down silos and turbocharge productivity in the workplace. But at what cost?

The basics of a data leak: definition and key facts

Any time restricted data is inadvertently released, that’s a data leak. The organization comes under attack from a bad actor who wants to steal that information. Data leaks happen through negligence or oversight, and don’t always require an attack to trigger them.

Modern enterprises have safeguards and security tools in place to shield against data breaches. But many organizations still overlook the risk posed by modern internal collaboration platforms. And that can have disastrous consequences.

Data leak vs. data breach

Most data leaks pose a small but manageable risk to a company’s finances, brand reputation, and employee trust, while a data breach is a data leak that has spiraled out of control. A data breach’s effects on the company create significant costs that threaten the company’s very survival.

Because no two companies are exactly alike, a data leak for one company might be a breach for another, based on company size, finances, and resources. A large, established company might be able to weather large fines, lost customer confidence, and lawsuits, but a small startup might go under from just a couple minor data leaks. But for both enterprise and smaller players, catching and repairing a leak should be a top priority, because the consequences of a leak-turned-breach can be severe. Both data leaks and breaches can come from within an organization, often resulting from an accidental employee mistake. Not all data leaks result from employee negligence, though. For example, an insider might maliciously share data with a third party. To be clear, 80% of incidents are not malicious, but regardless of intent, leaks have the potential to balloon and take your business down.

Leaks don’t get the same airtime and attention as breaches. We often hear about big data breaches that make headlines and cost companies millions. Data leaks, while smaller, can still cause serious pain, especially for those working in the security space. With the recent December 2023 SEC regulation updates, you may need to report even small leaks if they significantly alter the overall security reputation of your company.

What causes data leaks?

While data leaks are often associated with hackers or high-stakes espionage, most incidents stem from everyday mistakes and overlooked security gaps. These breakdowns in data protection can affect organizations of any size, and the most common causes include:

Software misconfiguration

Misconfigured applications, cloud storage buckets, or access settings remain the leading cause of data loss. In 2021, for example, UpGuard uncovered a Microsoft Power Apps misconfiguration that publicly exposed 38 million records. As organizations rely more heavily on cloud services, it’s important to closely monitor configurations as nearly 60% of breaches involve a human element through error, manipulation, or malicious misuse that can result in reputational damage.

Weak or reused passwords

Default, simple, or recycled passwords create easy entry points for attackers. This risk is amplified in environments with many Internet of Things (IoT) devices—such as smart thermostats, fitness trackers, or connected appliances—that often share the same network as corporate systems. A single weak credential can provide unauthorized access to sensitive data and increase the likelihood of accidental exposure.

Social engineering and credential scams

Attackers frequently target people rather than systems because it’s often faster and easier. Social engineering scams—such as phishing emails, text messages impersonating executives, or fake IT alerts—trick employees into handing over login credentials or sensitive information. These tactics effectively turn unsuspecting users into an insider threat, where a message appearing to come from a CEO requesting financial details or from “IT support” urging a password reset can quickly open the door to a major data leak.

Common data leak risks: protect your sensitive information

The term “data leak” can seem pretty broad. What specific kinds of information might be part of a data leak? Most data involved in leaks has the potential to compromise your organization’s customers, employees, and proprietary internal knowledge:

• Customer data: Phone numbers, addresses, emails, credit card numbers, social security numbers, and other personally identifiable information
• Internal employee data: Addresses and emails as well as human resource information like background checks, passport scans, and compensation data
• Intellectual property: Research, trade secrets, internal documentation, and source code
• Security credentials: Passwords or phone numbers for multi-factor authentication (MFA)

Are data leaks serious?

Not all the information disclosed in a data leak will be critical for the organization. However, the presence of the leak is itself a serious problem. The average data breach costs $3.92 million to mitigate, and 280 days to detect and contain. Some of the consequences of data leaks include:

• Loss of client or customer trust
• Regulatory fines
• Operational downtime
• Competitors accessing intellectual property

Because data leaks are usually the result of negligence or oversight, they can cause more damage to the company’s reputation than a targeted attack by malicious actors. Yet most companies spend far more time and resources defending against hackers. It’s easy to overlook the training and technology that could prevent accidental leaks.

What do cybercriminals look for in leaked data?

Cybercriminals target leaked data because it offers direct financial value, operational insight, or opportunities for further exploitation. This is why strong data leak prevention strategies are essential for organizations handling sensitive information. Common types of data they seek include:

Personal Identifiable Information (PII)

Names, addresses, national IDs, Social Security numbers, birthdates, and other identity markers that can be used for impersonation, credit fraud, or selling full identity profiles on illicit markets. Because PII is often stored without sufficient data encryption, it becomes an easy target for attackers.

Financial information

Credit card numbers, bank account details, transaction logs, and billing records that enable unauthorized purchases, wire transfers, or resale on the dark web. These types of assets are frequently linked to major financial loss when compromised.

Login credentials

Usernames, passwords, MFA backup codes, and session tokens that attackers exploit for account takeover. Many cybercriminals also use credential stuffing to test stolen passwords on other services, leading to broader cybersecurity exposure.

Health and medical records

Patient histories, insurance data, diagnoses, and prescriptions—valuable assets used in medical identity fraud, insurance scams, or blackmail. Attackers often exploit healthcare environments because they struggle with complex cloud security requirements.

Trade secrets and intellectual property

Product designs, research data, formulas, contracts, source code, or internal strategies that can be weaponized for competitive or nation-state espionage. These materials include confidential data that can shift market advantage when stolen.

Emails and internal communications

Sensitive conversations, negotiations, attachments, executive correspondence, or HR discussions that attackers can use for blackmail, extortion, or crafting highly tailored phishing emails. These messages may also reveal vulnerabilities that malicious insiders can exploit.

How do cybercriminals use leaked data?

Once cybercriminals obtain sensitive data, they can weaponize it in multiple ways—from direct monetization to launching more advanced attacks. The impact often extends far beyond the initial breach, turning a single security incident into sustained exposure.

Direct financial gain

Stolen data is frequently sold on dark web marketplaces or used to commit fraudulent transactions, open credit lines, or drain bank accounts. This is one of the most common outcomes of a cyber attack involving leaked data.

Phishing and social engineering campaigns

Detailed personal data or organizational information allows attackers to craft convincing emails or messages that trick users into revealing credentials, downloading malware, or approving unauthorized actions.

Ransomware and extortion attacks

Threat actors may use leaked data to pressure victims into paying ransom, threatening to publish sensitive files or expose customer information if demands aren’t met.

Identity theft and account takeover

Criminals can impersonate individuals to open new financial accounts, access government services, or take over social media, email, and business applications.

Facilitating broader criminal activity

Stolen identities and financial records can support money laundering, tax fraud, synthetic identity creation, and other illegal enterprises.

Reputation damage and operational disruption

For high-profile businesses or individuals, the exposure of internal communications or confidential documents can harm brand trust, trigger regulatory consequences, or create long-term public relations crises.

As threat actors evolve their methods, organizations must treat leaked data not as a one-time event but as a catalyst for downstream risk—reinforcing the need for continuous security monitoring and robust DLP controls.

Data leakage examples

Many companies have experienced leaks like those described above. A few key examples from industry leaders highlight just how much harm data leakage can cause.

Boeing

Global aerospace company Boeing experienced a leak when in 2017 one of its employees emailed a spreadsheet to his wife, a non-employee. He hoped that she could help him with some formatting issues, but he didn’t realize that the spreadsheet included personal data of 36,000 Boeing employees within hidden columns.

By emailing the spreadsheet to an unsecured device and non-employee email account, he went around security protocols and compromised the employee IDs, place of birth, and social security information of his coworkers.

Boeing said it was confident that the data stayed limited to the employee’s device and his wife’s, but it did offer all affected employees two years’ worth of free credit monitoring — an estimated cost of $7 million.

Microsoft

Software giant Microsoft experienced firsthand what can happen from careless mistakes.

In August 2022, cyber security firm spiderSilk noticed leaked login credentials in Microsoft’s Github environment. If cyber criminals had found the credentials, they could have been the entry point to access Microsoft’s Azure servers and possibly other internal systems.

The effects of exposed Microsoft data and source code could have been catastrophic for the organization, its customers, and its employees. Although Microsoft didn’t disclose the specific systems the credentials gave entry to, if outsiders had gained access to European Union customer information, Microsoft could have received a fine of up to €20 million for violating GDPR regulations.

Upon further investigation, Microsoft confirmed that no one accessed the data and is implementing new safeguards to prevent another leak.

Amazon

Many companies rely on AWS products, including Amazon S3, but incorrect configurations of S3 buckets have led to leaks. For example, in 2019, researchers at firm vpnMentor found a publicly available s3 bucket full of data from the human resources departments of multiple UK consulting firms. These files included sensitive personnel information like passports, tax documents, background checks, dates of birth, and phone numbers.

How to prevent data leaks

The majority of data leaks are caused by human error. That means they need human solutions. Training staff on the proper procedures for accessing or sharing information should be an ongoing process. Having new hires watch an hour-long video during onboarding won’t cut it. As technology evolves — and scammers become more sophisticated — the steps to prevent a leak must be updated.

Routine refresher courses on best data security practices should be part of your organization’s normal business operations. Create clear policies on how to handle information, where to store passwords, and what to do to validate an unusual request.

The shift to remote work during the pandemic dramatically increased the risk to organizations. The overnight adoption of new technologies created large holes in digital security. Faced with unprecedented upheaval, employees were left unsure how to protect themselves or their organizations. With remote work here to stay, businesses need to review their current tech stack to identify and close potential points of entry.

Collaboration platforms and data leaks

In tandem with improved security awareness training for employees, businesses should also provide their staff with the right tools to safeguard their information. There might be no clean desk policy for remote work, but security is still mission critical. Employees should know the procedures for how to store passwords, access company files, and share information.

Password managers, VPNs, centralized storage solutions, and SSO/zero trust can all help to secure confidential information within the remote workplace. However, there is one common place where information is freely shared, and outsiders are often invited to participate. That’s your digital collaboration platform.

Integration risks across collaboration ecosystems

The goal of collaboration is to break down internal silos and democratize information access. The faster and easier it is for people across the organization to communicate, the better they can all do their jobs. To facilitate easier information-sharing, collaboration platforms can plug into any number of other programs.

Slack enables hundreds of different integrations, from project management and productivity tools to file sharing, social media, and games. It’s the same story with Microsoft Teams and Workplace from Meta. Even Yammer allows about a hundred third-party apps to connect to your remote office.

Each of these applications exposes your online workplace to new vulnerabilities. A breach of one could open a back door to all the information shared across your collaboration network.

Third-party access and external collaboration risks

Another concern for businesses using collaboration is third-party user access. Slack Connect allows users to invite clients, contractors, and vendors into the workplace Slack environment to make it even easier to communicate and share documents. Similar functionality exists across most collaboration platforms, including Teams Connect, Workplace multi-company groups, and Yammer external groups.

Allowing third parties access to company collaboration platforms has proven benefits for the business. It can accelerate projects, strengthen working relationships, and produce better outcomes for all parties. But it doesn’t come without risk. Business relationships can change, and when they end you don’t want old documents, IP, and other sensitive information to remain in a single shared repository.

Security inconsistencies across shared environments

Even if you remain on good terms with a business partner in a shared collaboration space, how can you be sure that their security policies match your own? Have they written down or shared their access details with a third party, such as a contractor working on their behalf? How would you know if they had? And how can you be sure that every actor within your collaboration ecosystem is taking steps to safeguard the confidential information shared within its network of messages and chats.

How Mimecast can help prevent data leaks in collaboration

Many potential data leaks can be prevented by implementing a single, secure monitoring solution. Our platform connects to all major collaboration networks via API and webhooks, meaning no additional IT lift is required. From there, you can set policies that apply across your collaboration ecosystem and we will take care of implementation.

Continuous uploading means we capture the full context of collaboration in near real-time, including revisions and deletions. Other collaboration security tools rely on batch ingests to record data, resulting in lost information and incomplete context. Only we can deliver a complete, 360-degree contextualized oversight of activity within collaboration.

Then we take collaboration security a step further, with automated conversation monitoring using AI/ML-infused insights trained to understand short-form collaboration messages. Our natural language processor is best-in-class for collaboration, because it was built and trained specifically for this task.

Get authentic insights into insider risk and employee sentiment tot understand where risk exists within your collaboration environment. We empower some of the world’s biggest organizations to get proactive about collaboration data security.