Best practices for email signature security

Email signatures are often seen as a branding tool, but they also play an important role in cybersecurity. When left unmanaged or unsecured, email signatures can become a vulnerability. They expose companies to risks like phishing, data breaches, and impersonation. Phishing attacks account for over 60% of all data breaches according to Verizon’s 2023 Data Breach Investigations Report. These attacks often use compromised email signatures to make fraudulent messages appear legitimate. 

In this blog, we’ll explore best practices for email signature security, ensuring that your company’s email communications remain professional, consistent, and secure. 

Why is email signature security important? 

Email signature security plays a key role in protecting an organization from cybersecurity threats while also maintaining professionalism and compliance. Here’s why it matters: 

Preventing phishing and spoofing

Unsecured email signatures can be exploited by attackers to impersonate employees, leading to phishing attacks. By securing email signatures, organizations reduce the chances of their emails being spoofed, which protects employees, customers, and partners from becoming victims of fraudulent messages. 

Protecting data

Email signatures contain personal and business information like names, job titles, and phone numbers. If this data isn’t secured, it can be intercepted or tampered with, leading to data breaches or misuse of sensitive information. 

Keeping control of your brand

Consistent and secure email signatures make sure that every communication reflects the company’s brand and professionalism. Unsecure email signatures can allow unauthorized changes by third parties, potentially harming the company’s reputation and creating confusion for recipients. 

Complying with regulations

Many industries like healthcare and finance, have strict regulations about how personal information is handled. This is also true on a regional level, with 137 out of 194 countries now having privacy laws in place. Secure email signatures with necessary disclaimers help organizations remain compliant, avoiding potential legal issues and fines. 

Staying trustworthy and credible

A well-managed and secure email signature conveys professionalism and trustworthiness. Ensuring that email signatures are secure and standardized across all departments helps maintain the trust of customers and partners. 

Human error as a security risk 

Human error is one of the most significant vulnerabilities in email signature security. While technology is critical for securing email signatures, their effectiveness often depends on the people using them, who are often the weak link in the cybersecurity chain.  

Here’s how human error can play a part in compromising an organization’s security through emails and email signatures: 

1. Phishing and social engineering attacks 

Despite the best technical defenses, attackers frequently exploit human behavior to compromise email security. Phishing emails are designed to trick users into giving away their login credentials, leading to unauthorized access to critical systems. Once inside, attackers can alter email signatures to impersonate employees, launching further cyberattacks using compromised accounts. 

A phishing email that appears to come from the CEO might direct employees to access malicious links within their email signatures. This could cause employees to unknowingly pass malware along to clients or partners, which could have a catastrophic impact on your brand trust. 

2. Unintentional misconfiguration 

When employees manually update their personal email signatures, errors are likely. They might forget to include legal disclaimers, remove important company details, or inadvertently use old or out-of-date contact information.  

At best, this leads to confusion; at worst, it can end up with legal risks and reputational damage. It can also make phishing or spoofing attempts easier to pull off, because attackers can exploit those inconsistencies. 

3. Insecure email signatures

Email signatures often contain personal details such as names, job titles, phone numbers, and email addresses. If employees send messages using unsecured or improperly configured signatures, sensitive information can be exposed to unauthorized parties. 

To combat human error as an email signature security risk, training, awareness, and clear processes for managing signatures are vital. Alongside this, centralized email signature management is a fool-proof way to protect against all manner of email signature mistakes.  

10 best practices for email signature security 

Here are some best practices for email signature security that can help protect your organization from potential risks: 

1. Centralized email signature management 

Use a centralized email signature management platform to standardize signatures across your entire organization. 

This means that only authorized individuals or teams can make updates or changes to email signatures, minimizing the risk of human error and unauthorized modifications. 

2. Consistent application across devices and platforms 

Ensure signatures are consistent across all web-enabled devices and email platforms, such as Microsoft 365 and Google Workspace. This avoids discrepancies that attackers could exploit. 

Implement an email signature management solution that applies signatures server-side, rather than relying on individual devices to prevent bypasses. 

3. Include necessary legal disclaimers 

Add legal disclaimers in your email signatures, especially if required by law in your region or industry. These help to protect your organization from liability and data breaches. Make sure these disclaimers are kept up-to-date and consistent in all outgoing emails. 

4. Email authentication and encryption 

Implement email authentication protocols like SPF, DKIM, and DMARC to verify sender identities and reduce the risk of email spoofing. 

Encrypt emails that contain sensitive information to protect the content from unauthorized access, particularly in regulated industries, and industries where confidentiality is crucial like healthcare. 

5. Monitor and audit signature use

Regularly audit and monitor email signatures for any unusual changes or signs of tampering. 

Track who has access to your email signature management platform and periodically review permissions to prevent unauthorized access or misuse. 

6. Educate employees on signature security 

Train employees to recognize phishing attempts, especially those involving email signature impersonation or misuse.  

Emphasize the importance of not modifying email signatures and reporting any suspicious changes immediately. 

7. Implement multi-factor authentication (MFA) 

If you have an email signature management platform, ensure that it’s protected by MFA. This adds an extra layer of security to prevent unauthorized users from accessing and altering email signatures. 

8. Use secure links for external content 

If your email signature includes external links, make sure these use HTTPS links to avoid man-in-the-middle attacks. Avoid using shortened URLs, as they can obscure the destination and trick recipients into clicking malicious links. 

9. Personal information minimization 

Include only necessary information in email signatures. Avoid adding sensitive details like personal phone numbers that could be exploited if compromised. In industries where privacy is a concern, consider anonymizing certain details when not needed. 

10. Regularly update and review email signature policies 

Periodically review email signature policies to ensure they reflect current cybersecurity standards, legal requirements, and branding guidelines. Make sure all employees are aware of updates and best practices regarding email signature security and usage. 

By following these best practices, your organization can minimize security risks associated with email signatures, ensure compliance, and maintain trust in their communications. 

Case studies 

Here are a few well-known case studies that highlight the serious consequences of security lapses in organizations, particularly related to email and communication vulnerabilities: 

1. Sony Pictures hack (2014) 

Sony Pictures was the victim of a massive cyberattack, where hackers gained access to the company’s network, stole confidential data, and leaked private emails, scripts, and employee information. The hackers used phishing attacks and poor internal email security as key entry points. 

Impact: 

• Sensitive employee information, including Social Security numbers and health information, was exposed. 

• Corporate secrets, confidential contracts, and unreleased films were leaked. 

• The company faced significant reputational damage, legal ramifications, and financial losses. 

Weaknesses in email security like this can lead to significant breaches of confidential information. This highlights the importance of strong encryption, secure communication, and proper email signature management to prevent phishing and data loss. 

2. Target data breach (2013) 

Target suffered one of the largest data breaches in history, where hackers gained access to the credit card details of over 40 million customers. The breach was initiated through a phishing email sent to an HVAC vendor that worked with Target. This allowed attackers to access Target’s network through a poorly secured third-party connection. 

Impact: 

• 40 million credit and debit card accounts were compromised, with personal information of 70 million customers exposed. 

• Target had to pay over $18 million in settlements and faced class-action lawsuits. 

• The company’s reputation took a massive hit, causing a temporary drop in sales and customer trust. 

This breach underscores the importance of securing email communications with third-party vendors and partners. It shows how important it is for vendors to have proper security protocols in place. Vulnerabilities in one part of the email chain can expose an entire network. 

3. Maersk Ransomware Attack (2017) 

Global shipping giant Maersk was hit by the NotPetya ransomware, which exploited weaknesses in their network. The ransomware spread through phishing emails and software vulnerabilities, disrupting operations worldwide. 

Impact: 

• Maersk was forced to reinstall 4,000 servers, 45,000 PCs, and 2,500 applications, causing massive operational disruptions. 

• The total cost of the attack was estimated at $300 million. 

• Maersk’s ability to move cargo around the world was halted for weeks, damaging customer trust and causing significant revenue loss. 

This case emphasizes the need for robust email security protocols to prevent ransomware from spreading through email attachments or phishing. Regular system updates and having a secure, centralized email signature management platform can prevent hackers from spreading malicious software. 

Secure your company’s communications 

Email signatures may seem like a small part of your company’s communication, but they can be the first line of defense against phishing, spoofing, and costly ransomware attacks. Make sure you’re not leaving your organization exposed by overlooking this critical piece of your email security strategy. 

At Exclaimer, we protect data at every stage. From including DevSecOps engineers when we build new products, to running advanced web application firewalls during processing and protecting gateways with active DDoS protection. As well as enforcing MFA with Google and Microsoft sign-in options for single sign-on (SSO). 

It means data is encrypted at every stage, with TLS offering security across the entire network, which we continuously scan to fix issues before they start. Read more here about how we protect your email communications. 

Keep your emails safe and secure by centrally controlling them on one platform. Sign up for a free trial of Exclaimer today or get a demo.