How to Identify and Avoid Malicious Email Attachments

Introduction

Not all emails are sent with good intentions. Malicious actors misuse email communication to spread malware and steal information for personal gain. One method cybercriminals use to target email users is through malicious email attachments. It's crucial to be aware of their potential dangers. This article explains what email attachments are and presents actionable tips and techniques to identify and deal with them.

Understanding Malicious Email Attachments

An email attachment is a file sent along with an email, such as an image, video, or document. It's considered malicious if it contains harmful software, such as malware, spyware, or ransomware. These files are designed to look legitimate to trick users into downloading them. The purpose is to gain access to data or hack the system. However, you can identify the patterns followed in such emails and the file names used for malicious attachments.

Common File Types Used to Send Malicious Content

It's important to understand which file types to be cautious of to protect yourself from becoming a victim of malicious email attachments.

• Executable Files (.exe)
  Be wary of executable files, as downloading them can infect your device. It's uncommon for an executable file attachment to be legitimate. Most safe email attachments contain files such as PDFs or images. If you receive an executable file in an email, it is most likely malicious.

• Script Files (.js, .vbs, .bat)
  Be cautious with script files. Scripts may execute commands that compromise your system. Always verify their source before considering opening them. Script files are text files that contain code or instructions to perform tasks such as automation or data processing. They are usually written in scripting languages such as JavaScript (.js), Python (.py), or VBScript. Downloading a script file may execute harmful code on your computer, potentially stealing sensitive information, installing malware, or altering system settings. However, not all scripts are harmful. Read the following section to learn how to identify whether a script is malicious or not.

Signs of a Malicious Email Attachment

Don't just rely on your email provider to identify threats. Regardless of its effectiveness, some harmful files manage to avoid detection and slip through the cracks. Google claims that it can block 99.9% of malicious email attachments, but cybercriminals continually refine their tactics. That's why it's important to remain vigilant and pay attention to the following signs:

• Unknown Sender
  If you receive an email attachment from an unknown sender, the best practice is to test the file for any malicious code.

• Poor Grammar and Spelling Errors
  Do you ever wonder why spam and phishing emails often contain grammatical and spelling errors? While it's true that some hackers are not proficient in English, some intentionally make these mistakes to trap gullible users. They might also aim to appear as non-native speakers to make their business offers seem legitimate.

• Strange File Names or Extensions
  Watch out for peculiar file names such as "Invoice.bat," "password_reset.zip," "UrgentActionRequired.exe," "1234.py," and "account_suspended.html."

• Files with Double Extensions
  A file name with more than one extension, such as .png.exe, is a warning sign of a malicious file. It's a common trick used by hackers to conceal the actual file type. However, you can identify the file type by looking at the last extension. In our example, ".png.exe" has .exe as the last extension, indicating the file is not an image but an executable file. So, the next time you receive a file with a dual extension, you'll know what to do.

Tools and Techniques to Identify Malicious Email Attachments

Want to shield yourself against the threats of malicious emails? The following tools and techniques can help you identify malicious email attachments. Incorporate them into your digital routine for a safer and more secure emailing experience.

• Use Antivirus Programs and Email Security Software
  Install a reputable and powerful antivirus program that provides the capability to scan email attachments for malware and viruses. It will alert you whenever you attempt to open any suspicious link or attachment. Remember to update your antivirus program regularly to ensure maximum security. Some popular antivirus software options include Bitdefender and Avast.

• Check Links Before Opening Them
  Always check where the link points before clicking on it. On a desktop, you can do this by hovering over a link, and its URL will be displayed in the bottom-left corner of the screen. On a mobile device, long-press a link to see its URL. Additionally, to verify whether the URL is safe, copy it (without clicking on it) and assess its safety by uploading it to a link checker website.

• Sandbox Suspicious Attachments
  Sandboxing is a technique to open or execute a potentially malicious attachment in a safe and controlled manner. A sandbox uses a virtual environment to ensure the actual system is not harmed in any way. It checks and monitors the file for malicious software or any dubious activity. If no threats are found, you can safely open the file. VirusTotal is a popular sandbox tool.

Email Security Best Practices for Organizations

For organizations, email security is pivotal in safeguarding sensitive data and preventing costly errors.

• Conduct cybersecurity training programs to raise awareness about email-related threats.

• Educate teams on identifying and handling suspicious emails and attachments.

• Enforce rules such as email filters, domain blocking, and use third-party tools for detecting malicious email attachments.

• Set up an email security gateway to monitor emails being sent and received, protecting against threats such as malware and phishing attacks.

How to Handle a Malicious Email Attachment

Exercise caution when dealing with dubious email attachments. Interacting with them can compromise your data and system security.

• Do not open the attachment
  Avoid downloading suspicious-looking attachments at all costs. If you are not cautious, the attachment can wreak havoc on your system and steal your information.

• Report the Email
  Do not interact with the email attachment. Report the email to your email provider or the IT department in your organization.

Made the mistake of downloading an attachment from an unknown source? If you accidentally download a suspicious attachment, don't panic. Follow these essential steps to mitigate the potential damage it can cause:

• Disconnect your device from the Internet.
• Do not open the file.
• Completely delete the file from your system, including the recycle bin.
• Use an antivirus program to conduct a full system scan. The scan will likely detect the malicious file and remove it from your device.
• Monitor your device or email account for any unusual activities or slow system performance.

Bounce Back Emails to Discourage the Sender

Often, hackers target you with malicious email attachments from multiple email addresses. You can bounce back such emails if they persist despite being ignored. Once the sender is tricked into believing their emails are not reaching your inbox, they will likely stop targeting you.

Curious how to send a bounce-back message? Block Sender has got your back! Block Sender is a robust blocking tool available for use both through its web dashboard and as a Gmail add-on. Just install it with a few simple steps to regain control of your inbox.

Block Sender provides the option to send bounce-back emails based on various criteria, such as bouncing back emails from a particular sender, email address, domain, or IP address, or emails containing a specific subject or phrases.

Here's how you can bounce back emails using Block Sender:

1. Log in to Block Sender.

2. Navigate to Blocks and click + New Blocking Rule.

3. Select a blocking criterion from the dropdown menu and enter precisely what you wish to block in the field next to it.

4. Decide where you want blocked emails to be sent, such as to the Trash, Delete, Archive, or Spam folder.

5. Select the option to bounce back the emails.

6. Click Create.

Conclusion

Educating yourself about the dangers of malicious emails is important. Take preventive measures and avoid interacting with any suspicious files sent in emails. Third-party tools, such as antivirus programs and email gateways, play a pivotal role in protecting you against the risks posed by malicious email attachments.