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Protecting Email from Attack in Office 365

Advanced Email Security for You and Your Business

Office 365 is the world’s most popular office productivity suite, with user numbers surpassing 100 million in 2017. With the vast amount of data shared via email in the Office 365 Suite, a critical question IT admins should be asking is: How secure is it?

The sophistication and instances of phishing and spear phishing attacks continue to rise, and organisations need to be ready to prevent infiltrations from every angle. With new threats emerging such as business email compromise, conversation hijacking and other social engineering efforts, it’s now clear that no single solution can keep you as safe as you need to be. And if you’re in a regulated industry, like healthcare or finance, the stakes to maintain data security are even higher.

When you buy into the idea of replacing multiple productivity solutions with a single suite –such as Office 365 – there is a clear reduction of cost and increase in efficiency. However, the suite doesn’t offer the layered security protection businesses need to safeguard data. While Office 365 comes equipped with native security features that protect data in a number of ways, customers need to look beyond what comes in the box and consider the liability that comes with too little protection.

This white paper will detail how companies can reduce the risk associated with email-based malware attacks in an Office 365 environment by implementing a layered security approach that includes policies and training, filtering and encryption services and security software.

Layer I: Policies & Training

A hacker only needs one person to click on their fraudulent link to access credit card, debit card and Social Security numbers, names, addresses, proprietary information and other sensitive data. One of the best defences against hacks is to establish consistent user training and implement and enforce polices regarding the handling of email.

Email policies should be created in a manner that reduces risk of an attack, while addressing your organisation’s specific challenges and goals.

Consider the following basic policies for internal emails:

  • Don’t send e-mail in HTML format
  • Don’t send unrequested attachments or hyperlinks
  • Don’t include or ask for personal information
  • Use the full name of the user

One way companies can help users minimise the risk of attack is to require a specific format for how each message is written. This provides an identifying element for users to verify each internal correspondence. If an internal email doesn’t follow that format and includes a link, it could serve as a red flag for something suspicious. While it’s possible the sender accidentally failed to follow the format, touch base with the sender. If the recipient can quickly IM or call the sender via phone to verify authenticity, a potential infiltration can be prevented.


A good place to begin to determine potential vulnerability is to establish a baseline of end user security practices. You can’t accurately fix a problem if you can’t quantify it. This seems like a no-brainer, however nearly 80% of organisations don’t conduct any sort of security testing. Here are some things to consider when implementing testing and training:

  • Penetration testing: Sending users suspicious—yet harmless— emails to gauge whether or not they open them, respond to them or click on links. Whether conducted by your IT department or through an independent solution provider, penetration testing is a good way to see how susceptible your organisation may be to attacks.
  • Follow-up: Should an employee improperly interact with an email during penetration testing, it’s critical to discuss the exercise as soon as possible and further emphasise best practices.
  • Quizzing: At random intervals throughout the year, implement brief, mandatory quizzes to test staffers’ knowledge of data management best practices. This can help determine how well policies are being followed and guide areas of training improvement.
  • Don’t forget phones: Many hackers are now turning to the phone to lay the groundwork for an attack. Cybercriminals will often pose as someone within the organisation, a customer or outside vendor and convince the employee on the line to open an email they’ve received. A phone conversation can build trust that couldn’t otherwise be gained by an email alone.

Security policies and training should be reviewed continuously to keep up with the changing threatscape. Consider both to be living documents in constant need of refinement to ensure vulnerability is minimised.

Layer II: Filtering and Encryption Services

The second layer of securing email in an Office 365 environment is implementing cloud-based filtering and encryption services. Policies and training can reduce the possibility of a phishing or spear phishing attack, but the risk is never eliminated without supporting technology that identifies and takes action against threats before reaching the actual network. After all, humans make mistakes and hackers are devising more sophisticated and unexpected ways to gain access to networks. Here’s what you should know about selecting point-to-point encryption, as well as appropriate and effective email security solutions.

Point-to-Point Encryption

Encryption is critical to a layered security approach because emails may contain sensitive data like Social Security numbers, credit card numbers and proprietary company information. Microsoft’s offering encrypts emails once it reaches the server, leaving it readable while in transit. To best protect emails, point-to-point encryption – which encrypts the message immediately – is necessary to protect the email throughout the entirety of its lifecycle.

But point-to-point’s benefits don’t end just with encryption. By clicking on a “send secure” button, the encrypted message will remain in the server, and the recipient will receive a message allowing them to access the email via a secure portal. In short, infected emails are never sent or received.

Advanced point-to-point encryption solutions offer secure recipient experiences in both mobile and desktop offerings, include client branding on emails to assist recipients in determining the validity/ source of the email, and provide true message recall, which allows the sender to “unsend” an email when needed.

Email and Web Filtering

Office 365 features some email filtering offerings, but they’re often not comprehensive enough to address most organisation’s needs. The default filtering settings provide potential holes for unwanted email, malware and phishing leaks, not to mention increased administrative burdens.

While the settings can be customised, doing so can be time consuming, especially when certain tasks have to be performed by end-users, which disrupts productivity – not good for a suite selling customers on productivity. For many companies, finding a email security service outside of Office 365 is a necessity. Here’s what you should be looking for in an email security service:

  • Greater admin control over group and individual access restrictions
  • Easy rules implementation to filter unwanted mail away from your inboxes
  • Reduction of clutter from known malicious and unwanted sources
  • Minimum of four anti-virus engines, continually updated
  • Built-in mechanism to handle bulk mail

Should an email get through with a corrupted link, web filtering – which isn’t offered by Office 365 – can provide another layer of defence to block malware from infecting your network. When considering a web filter, ensure it performs each of the following tasks:

  • Shields your network from a wide range of malware, ransomware, adware and viruses via email, web download and java script download.
  • Continuously monitor outbound traffic and sends real-time notifications if a malicious program is detected.
  • Maintain fast browsing experience to maintain productivity.
  • Updated thousands of times per day.

When email security and web filtering are both employed in a layered approach, sophisticated attacks can be stopped. Consider the following scenario:

  • An email with an embedded link is sent to someone in your organisation late at night – when they’re not checking email.
  • The link points to a clean Dropbox file, which has never been used in a previous attack.
  • Because it hasn’t been reported by any network monitoring programs your organisation uses, the typical email filter recognises it as safe and lets the email through to the intended user.
  • At some point between the email being sent and passing through the network’s filter, the malware provider changes the endpoint of the link, which leads the business user to malware when clicked.
  • The user gets up in the morning and the now-malicious email is waiting in their inbox, ready for action.

This issue is common and can be combatted with the right web filtering solution. While the email filter did what it was supposed to do, the hackers “tricked” the system by changing the link. Web filters with downstream monitoring will immediately notice when the link has been changed and redirect the email safely away from the user’s inbox. A layered approach will position your organisation to reduce the risk of email-related security issues to its absolute minimum.

Layer III: Security Software

While cloud-based filtering and encryption services can drastically reduce the risk associated with email security, it’s also important to have the right locally-installed security software to complement your filter – and in some cases serve as a final line of defence. Layered security is important because attacks come in all different forms and no solution can block them all.

For example: An anti-virus solution can block and quarantine infected files brought in via local media, whereas a network firewall cannot. A network firewall is instead intended to block attacks from outside the network. Layered security is the best way to protect businesses from attacks and their own users.

Here are other things you should look for in a locally-installed security software solution:

  • Anti-virus protection: This is the most common need. While cloudbased web and spam filters can keep most corrupted emails out, security software adds another layer of defence.
  • Content and image control: This can prevent potentially offensive material, which may also contain viruses, from getting through.
  • Scalability: As your security needs grow, your software solution should be able to adapt to avoid lapses in security


Hackers continue to find new ways to infiltrate networks and gain sensitive data via email, so it’s more important than ever to have the most comprehensive security platform possible. Within an Office 365 environment, a layered approach consisting of comprehensive policies and training, cloud-based filtering and encryption services and locally-installed security software – and hardware, depending on your organisation’s size – will dramatically reduce the risk of your business being the next victim of phishing, ransomware or other social engineering attacks. Learn how AppRiver can strengthen your layered security approach and help take the liability out of leaving your network unprepared.