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How Many Encrypted Attacks Use TLS to Hide Communications?

How Many Encrypted Attacks Use TLS to Hide Communications?

July 29, 2021 | Anastasios Arampatzis

Reports from Sophos, Venafi and Zscaler all point to prominent ways in which cybercriminals are increasingly leveraging TLS encryption to launch their nefarious attacks with great success. It is time to reflect on what causes this increase in encrypted attacks and review what we do to defend ourselves against these threats.

Sophos: Almost half of all malware is encrypted

The Sophos report findings centered on increase and diversity of attacks, their method strategy and the abundant use of TLS protected repositories as unwitting yet complicit parties in crime.

The key findings include:

  • TLS encrypted crime has doubled in the past yearnow at 46%, up from 23% in 2020.
  • TLS use extends to non-standard ports, and half of all malware on non-standard ports has CA-issued TLS certificates. A truly accurate accounting of all TLS-encrypted malware, therefore, requires further packet analysis of all communications.
  • TLS use in actual malware is low (2%), but 56% of the servers that communicated with malware were encrypted. Half of all malware communications go to servers in the US and India.

The report also highlights some trends:

  • TLS protected web and cloud services are prime launching places for nefarious encrypted attacks. Repositories such as Github, Discord and Google’s cloud services are being used to store malware, stash stolen information and send botnet commands.
  • TLS encryption is mostly employed in malware droppers leveraging TLS protection to access malware-hosting documents on websites such as Pastebin and GoogleDocs.
  • There is a growing industry of off-the-shelf security offensives, making out-of-the-box TLS encrypted attacks more sophisticated, agile and undetectable.
Venafi: The expanding attack surface

Venafi’s analysis of attacks over a five-year period (2014-2019) draws the following conclusions regarding the nature of encrypted attacks on machine identities and their various types.

  • A nearly 500% growth across three main machine identity threats—malware, vulnerabilities and cyberattacks—from 2014-2019.
  • Cyberattacks and APT attacks affecting machine identities are up 1600% over same period.
  • Businesses suffered between $51 and $72 billion USD in global economic losses due to unprotected machine identities.

The massive proliferation in the number and type of machine identities has triggered a corresponding increase in the machine identity threat attack surface, which has exploded over the last five years, as shown in the diagram below.


The Venafi report indicates the following trends regarding the three machine identity threats:

  • Vulnerabilities are up 260%. Vulnerabilities that involve machine identities have become increasingly common. “Malicious actors were able to access a server’s private encryption key—and just one exploit of this bug exposed 4.5 million patient records at the hospital group Community Health Systems,” says Yana Blachman, principal threat intelligence analyst at Venafi.
  • Malware is up 300%.  Sophisticated machine identity capabilities have become a larger part of the arsenal of “commodity” malware used in cybercriminal toolkits. Stolen and fraudulent TLS certificates, as well as code signing keys, have become a key element of the cybercriminal’s playbook. SSH keys are becoming prominent targets as they do not expire, and one key often provides multiple points of access.
  • APTs and cyberattacks up 1600%. Advanced Persistent Threats (APTs) are increasingly popular “because they support and enable persistence, lateral movement and defensive evasion,” according to Blachman. “By stealing ‘trusted’ machine identities from global technology companies, perpetrators of APTs can execute effective attacks that don’t raise any alarms until well after the damage is done,” adds Kevin Bocek.
Zscaler: 2020 state of encrypted attacks

As reported in a previous blog, Zscaler’s ThreatLabZ performed an in-depth analysis of millions of encrypted data communications over a nine-month period in 2020. Their key findings are summarized, below.

  • 80% of all internet traffic is now encrypted.
  • Healthcare is the most targeted industry for encryption-based attacks.
  • 30% of SSL-based attacks hide in popular cloud-based file-sharing services (AWS, GoogleDrive, OneDrive, Dropbox).

The key trends identified in the Zscaler report indicate the following:

  • Malicious URLs. Out of 1.69 billion encrypted attacks targeting the healthcare sector, 84.2 percent utilized malicious URLs
  • Fake Apps. By hitting “Accept” the user grants permissions to rogue or infected apps to scan, scope and infiltrate their device, often allowing the attacker to exfiltrate sensitive data gleaned from legitimate personal and banking apps.
  • Cloud Storage Attacks: The trusted status of popular and well-established cloud storage providers like Box and Drive is exploited for their “safe” access, under which malicious payloads are dropped, called for or linked to.
How to mitigate TLS criminal attacks

The three reports offer sound advice on the prevention of further encryption-based attacks. As the Sophos report sums up, “Without a defense in depth, organizations may be increasingly less likely to detect threats on the wire before they have been deployed by attackers.”

Part of the challenge noted by Zscaler is the overwhelming amount of encrypted traffic to be inspected—and tools widely in use that are unsuited to the scale of the task. For this reason, defense models rely on shortcuts (“trusted” sites) that are now being uncovered and exploited by the cyber underground. Therefore, the report advocates a “multilayered, defense-in-depth strategy that fully supports SSL inspection” to stay ahead of increasingly well-hidden encrypted threats.

Venafi identifies the three primary targets of machine identity attack; TLS, SSH and code signing, and suggests an all-encompassing strategy. “Venafi Trust Protection Platform currently is the only commercial enterprise solution on the market that provides a full lifecycle machine identity management platform for all machine identity types—even in large, complex networks.”


Fully automating any solution is best practice for mitigating the overwhelming amount of encrypted cyberattacks launched at machine identities daily. The sheer volume of unchecked encrypted communication sent over the wire daily is a large factor in how many attacks are being landed unawares. Employing an in-depth enterprise scale solution that monitors, renews and is omnipresent is an emerging necessity to securing your enterprise in a post-TLS exploited world.

Learn how Venafi can help your organization defend against encrypted attacks by contacting one of our experts.

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About the author

Anastasios Arampatzis
Anastasios Arampatzis

Anastasios Arampatzis is a retired Hellenic Air Force officer with over 20 years of experience in evaluating cybersecurity and managing IT projects. He works as an informatics instructor at AKMI Educational Institute, while his interests include exploring the human side of cybersecurity.

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