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How to Weed the Bad Links Out of Your Inboxes

• Mar 12, 2018

While malicious links are not a new cyberthreat, this tactic remains a pervasive and effective hacking technique.

For instance, with the Meltdown and Spectre vulnerabilities recently threatening billions of computers, many people, urgent to find information and solutions, clicked a link that arrived unsolicited in their inboxes, purportedly from the German Federal Office for Information Security. The link appeared legitimate and promised to provide a defense strategy. Instead, the very malware that those users were trying to avoid was installed on their computers.

Locky ransomware, originally released in 2016, offers a similar cautionary tale. Locky regained popularity in 2017 with more than 130 million emails being sent, peaking in September with 60 million emails delivering the malware in a single day. The infection spread via an otherwise innocuous-seeming email containing either an embedded link to a malicious site or an “invoice” attachment that contained the Visual Basic script of the malware downloader. In fact, this exploit proved to be so successful that the total cost of the Locky cyberattack has been estimated at more than $1 billion.

Both of these incidents highlight the scope and scale of malicious URLs. With attacks most likely to appear in organizations' inboxes and most likely to strike at the bottom line, entities need to understand both why these attacks are so common and how to combat them.

The Allure of Bad Links

The phishing tactics used to make malicious URLs and the emails that make them look entirely legitimate are diverse. For this reason, this forgery — such as using polished emails or websites that are SSL-enabled — is difficult to spot for even the most diligent users. While many users are aware that such links can be traps, many have nonetheless clicked these links before and likely will again.

In fact, 91 percent of all cyberattacks begin with a phishing email, indicating the fundamental risks these threats pose to organizations. So where does this disconnect between knowledge and practice stem from?

First and foremost, users are naturally curious. Links promising to connect a user with valuable information or a lucrative opportunity play into that vulnerability. Moreover, links that obscure the true destination with a "cousin domain" (a link that manipulates one or a few letters to mimic an authentic web address, such as adding or replacing a single letter) or with a link shortened by services like bit.ly, can deceive even the most cautious users.

With 97 percent of bit.ly links leading to malicious websites, this threat from shortened links is astonishingly high — namely because the link shortening circumvents the long-trusted "hover method," in which a user places his mouse over a link to see its destination before clicking it.

The Solution to Bad Links

Exacerbating the above problems are two drivers of employee success: efficiency and productivity. Scrutinizing every link in every email takes time, particularly with the average worker getting 121 emails per day. Workers may worry that not clicking a potentially legitimate link that contains important files or information could result in lost productivity and employer blowback.

While no single solution to this complex problem exists, businesses can better protect themselves and their users by relying on a comprehensive defense strategy that prioritizes security and convenience.

Link filtering. Scanning emails for embedded links that go to known malicious websites, newly registered domains, or those with low or no reputation, and quarantining them before they reach the user’s inbox should always be the first line of defense.

Cousin spotting. Hackers will often register domains “similar” to popular websites or the company they are attacking and then host their malicious code from them. These “cousin domains” typically have a single letter changed or added, making them seem legitimate enough to avoid detection, especially by users working quickly. Having a solution that validates domains and safeguards users against visiting the spoofed URLs is a strong second line of defense.

Time-of-click analysis. One way hackers bypass basic security measures is by emailing legitimate links and then compromising those sites to host their malicious software. As the links represent older, trusted domains, they often pass through inbound filters. Having a tool that analyzes links in real time confirms that a destination is safe anytime a user clicks on it. This ensures that even if a site is later compromised, the system will analyze the end destination and make sure it’s safe to visit prior to letting the user visit it.

Link scoring and restoration. A link-scoring feature in a cybersecurity tool ensures that securing the email inbox does not create unnecessary business interruptions. If the tool determines the link to be legitimate, for instance, it automatically sends users to their destination. If the link is suspicious, however, the tool provides users with clear information about why caution is necessary and how best to proceed. Moreover, the convenience of shortened links does not outweigh their risks. Links that automatically restore to full length, negating any uncertainty about their destinations, are an invaluable asset to users.

Banner announcements. Still, organizations should ensure that link analysis does not happen behind the curtain, so to speak. In order to continue raising awareness about the risk of links and educating users on best practices, every link should display a banner announcing that it is being analyzed for security at the time of click. By foregrounding this vetting process with a bold banner, organizations teach users not to become flippant about the links in their inboxes and to keep the threat top of mind.

While educated and astute users are a good line of defense for any organization, relying on them alone will not stop the problem of malicious URLs. This cyberthreat is simply too sophisticated and too targeted, but because it relies on human exploits rather than machine exploits, smart tools can unmask what users may miss. Protect yourself by unburdening your users, and take the hackers out of the equation this year.