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Security: Article

Switching the Locks: Who Has Copies of Your SSH Keys?

Organizations are constantly leaving themselves open to security breaches and noncompliance with federal regulations

Despite the recent flood of high profile network breaches, hacking attempts are hardly new. In 1995, I was attending school in Helsinki when I discovered a password "sniffer" attack in our university network. In response, I wrote a program called the "secure shell" to safeguard information as it traveled from point to point within the network. This new program shielded all of our data and ensured that these kinds of attacks didn't jeopardize our logins.

This program, SSH, works by developing an encryption key pair - one key for the server and the other key for the user's computer - and encrypting the data that is transferred between those two keys. Currently, almost every major network environment - including those in large enterprises, financial institutions and governments - uses a version of SSH to preserve data in transit and let administrators operate systems remotely. Organizations use SSH to encrypt everything from health records to logins, financial data and other personal information.

Management of Keys a Low Priority
Despite the fact that SSH keys safeguard extremely sensitive information, companies have been incredibly casual at managing SSH key generation, access and location throughout their network environments. It's similar to a home security company making numerous copies of a person's housekeys, throwing them all over the streets and never changing the lock. The only things needed to pick up one of these keys and use it to access encrypted data are interest, time and a little know-how.

Organizations are constantly leaving themselves open to security breaches and noncompliance with federal regulations by not being more diligent about SSH key management. Many are incapable of controlling who creates keys, how many are created, or where they are positioned in the network after being dispensed and those discrepancies will lead them to network-wide attacks.

Swept Under the Rug
The issue has remained concealed in the IT department, guarded by its vastly technical nature and frequent organizational challenges. System administrators may not appreciate or understand the full scope of the problem because they typically only see a small piece of their environment. On the other side of the company, even if executives and business managers recognize that there is an issue, they are usually too busy to evaluate its scope or possible implications.

SSH key mismanagement is as mysterious as it is widespread. Through dialogs with prominent governments, financial institutions and enterprises, we have determined that on average most companies have between eight and over 100 SSH keys in their environments that allow access to each Unix/Linux server. Some of these keys also permit high-level root access, allowing servers to be vulnerable to "high-risk" insiders. These "insiders," including anyone who has ever been given server access, can use these mismanaged SSH keys to gain permanent access to production servers.

Mismanaged SSH Keys Give Viruses the Advantage
Each day, the probability increases of such a breach occurring. Attacks are becoming more prevalent and sophisticated, and news stories about network breaches are popping up daily. Using SSH keys as an attack vector in a virus is very easy, requiring only a few hundred lines of code. Once a virus secures successful entry, it can use mismanaged SSH keys to spread from server to server throughout the company.

Key-based access networks are so closely connected that it is extremely likely that a successful attack will travel through all organizational servers, especially if the virus also uses additional attack vectors to increase privileges to "root" after breaching a server. With the high number of keys being distributed, it is likely that the virus will infect nearly all servers within minutes, including disaster recovery and backup servers that are typically also managed using such keys.

In the worst case scenario, a virus utilizing numerous attack vectors could spread Internet-wide, rapidly and, combined with dissolution technologies, could corrupt enormous quantities of data.

Industry Regulations Flouted
Organizations lacking proper SSH key management protocols are not only vulnerable to security breaches, they are also out of compliance with mandatory security requirements and laws. SOX, FISMA, PCI and HIPAA are all industry regulations that require control of server access as well as the ability to discontinue that access. Additionally, companies may also be disregarding internal security practices (in some cases, policies mandated by customers).

The SSH protocol and its most commonly used implementations do not create these risks. Rather, it is the result of faulty protocols relating to SSH keys, inadequate time and means to research the problem to develop solutions, lack of understanding of the implications of the issue and the hesitancy of auditors to flag problems that they do not have solutions for.

Clearly the issue of SSH keys being improperly managed cannot be glossed over forever. Without auditing, controlling, or terminating SSH key-based access to their IT systems and data properly, most healthcare providers, enterprises and government agencies are easy targets for an attacker.

Steps to Combat the Risks
Before steps can be taken to solve a problem, it must be identified as a legitimate issue. It may take multiple IT teams to begin a remediation project and will require proper endorsement and support within the company.

There are multiple steps that make up the core of the remediation project:

  • Automating key setups and key removals; eliminating human errors, manual work and reducing the amount of administrators from hundreds to almost none.
  • Controlling what commands can be executed using each key and where the keys can be used from.
  • Enforcing proper protocols for establishing keys and other key operations.
  • Monitoring the environment in order to determine which keys are actively in use and removing keys that are no longer being used.
  • Rotating keys, i.e., switching out every authorized key (and corresponding identity keys) on a regular basis, so that any compromised (copied) keys stop working.
  • Unearthing all current trust-relationships (who has access to what).

The Future of Security
SSH continues to be the gold standard for data-in-transit security but the management of SSH network access must be addressed by organizations in the current threat landscape.

Nearly all of the Fortune 500 and several prominent government agencies are inadvertently putting themselves at risk to major security threats from hackers or rogue employees because they continue to operate out of compliance. This problem cannot be solved overnight. It will take numerous years and thousands of well-trained people to fully combat the problem. It must be the entire organization's responsibility to address the issue. Time must be allotted and it must become a priority to ensure that SSH user keys are properly managed in their companies.

More Stories By Tatu Ylönen

Tatu Ylönen is the CEO and founder of SSH Communications Security. While working as a researcher at Helsinki University of Technology, he began working on a solution to combat a password-sniffing attack that targeted the university’s networks. What resulted was the development of the secure shell (SSH), a security technology that would quickly replace vulnerable rlogin, TELNET and rsh protocols as the gold standard for data-in-transit security.

Tatu has been a key driver in the emergence of security technology, including SSH & SFTP protocols and co-author of globally recognized IETF standards. He has been with SSH since its inception in 1995, holding various roles including CEO, CTO and as a board member.

In October 2011 Tatu returned as chief executive officer of SSH Communications Security, bringing his experience as a network security innovator to SSH’s product line. He is charting an exciting new course for the future of the space that he invented.

Tatu holds a Master of Science degree from the Helsinki University of Technology.

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