Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Vulnerabilities / Threats

10/22/2015
03:50 PM
Connect Directly
Twitter
LinkedIn
RSS
E-Mail
50%
50%

Undermining Security By Attacking Computer Clocks

A team of researchers at Boston University has developed several attacks against the Network Time Protocol that is used to synchronize internal computer clocks on the Internet

Researchers at Boston University have uncovered several vulnerabilities in the Network Time Protocol (NTP) that is used to synchronize the internal clocks on millions of computers worldwide.

The vulnerabilities, now patched, give attackers multiple ways to change the clock settings on systems that use NTP so as to seriously disrupt applications and services that are dependent on accurate time to function securely.

NTP has been used since 1985 to synchronize time between systems that communicate with each other over a network. With NTP, a global network of systems, serve as the primary timekeepers on the Internet. Tens of millions of client systems query these servers on a periodic basis to ensure that their internal clocks are in synch with the time maintained by the primary servers.

In a paper released Tuesday, researchers Aanchal Malhotra, Isaac Cohen, Erik Brakke, and Sharon Goldberg described several scenarios in which an attacker could take advantage of vulnerabilities in NTP to alter the clocks on client systems relatively easily and with potentially severe consequences.

For example, setting the clock back on a client to a previous point in time could cause the system to accept rogue Transport Layer Security (TLS) certificates that may have been already revoked, thereby giving attackers a way to decrypt encrypted communications.

Similarly, an NTP attack sending a primary server forwards in time could cause timestamps on DNSSEC cryptographic keys and signatures to expire, causing the server and all its clients to lose connectivity to domains secured with DNSSEC, the researchers said in their paper.

As an example of the problems that can result from incorrect time information, the paper highlights one incident in November 2012 when NTP servers at USNO.NAVY.MIL incorrectly started listing times from the year 2000, causing outages of Active Directory Servers, authentication systems and routers.

The BU research paper outlines four methods that attackers can employ to compromise NTP.

One of the methods is to disable NTP on a client system by taking advantage of a safety mechanism in NTP called the Kiss of Death (KoD) packet, the researchers said.

The mechanism is normally used when a client system begins sending too many queries to the NTP server, either because of a malfunction or because it has been compromised. In such situations the KoD packet is used to stop the client from querying the server for a period of time.

According to the researchers, some older versions of NTP make it easy for an attacker to spoof KoD packets so they appear to be from a legitimate NTP server and then send them to a client system. This can cause the victim system to stop querying its NTP servers for days or even years, throwing off the internal clock seriously in the process. 

Only a few spoofed KoD packets are needed for the attack to work so it is relatively easy for threat actors to target systems in bulk by adapting network scanning tools to send the spoofed KoD packets, the researchers noted.

A second attack method described in the paper also takes advantage of the KoD mechanism. But in this case, attackers send NTP servers a high volume of queries that are spoofed to look like they came from a particular client system. This prompts the server to issue a KoD packet effectively blocking the client system from sending further queries for sometime.

One of the other attack methods involves hijacking traffic to NTP servers while the fourth method described in the report takes advantage of packet fragmentation in iPV4 to shift time on client systems.

The attacks are mainly possible because of poor authentication of NTP messages, the researchers said in their report. Though mechanisms exist to cryptographically authenticate NTP messages that are sent between clients and servers, they are rarely implemented. As a result, it is trivially easy with some versions of NTP to spoof the messages, Malhotra and the other researchers said.

The researchers have listed fixes and workarounds for each of the four attack methods described in their paper.

Black Hat Europe returns to the beautiful city of Amsterdam, Netherlands November 12 & 13, 2015. Click here for more information and to register.

Jai Vijayan is a seasoned technology reporter with over 20 years of experience in IT trade journalism. He was most recently a Senior Editor at Computerworld, where he covered information security and data privacy issues for the publication. Over the course of his 20-year ... View Full Bio
 

Recommended Reading:

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
RyanSepe
50%
50%
RyanSepe,
User Rank: Ninja
10/23/2015 | 1:09:30 PM
Fingerprinting NTP
Interesting. Typically, are these KoD and malformed packets sent on a large scale basis using zombie machines or are these more of targeted attack after an NTP server has been fingerprinted?
Commentary
Ransomware Is Not the Problem
Adam Shostack, Consultant, Entrepreneur, Technologist, Game Designer,  6/9/2021
Edge-DRsplash-11-edge-ask-the-experts
How Can I Test the Security of My Home-Office Employees' Routers?
John Bock, Senior Research Scientist,  6/7/2021
News
New Ransomware Group Claiming Connection to REvil Gang Surfaces
Jai Vijayan, Contributing Writer,  6/10/2021
Register for Dark Reading Newsletters
White Papers
Video
Cartoon Contest
Write a Caption, Win an Amazon Gift Card! Click Here
Latest Comment: Zero Trust doesn't have to break your budget!
Current Issue
The State of Cybersecurity Incident Response
In this report learn how enterprises are building their incident response teams and processes, how they research potential compromises, how they respond to new breaches, and what tools and processes they use to remediate problems and improve their cyber defenses for the future.
Flash Poll
How Enterprises are Developing Secure Applications
How Enterprises are Developing Secure Applications
Recent breaches of third-party apps are driving many organizations to think harder about the security of their off-the-shelf software as they continue to move left in secure software development practices.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2020-25414
PUBLISHED: 2021-06-17
A local file inclusion vulnerability was discovered in the captcha function in Monstra 3.0.4 which allows remote attackers to execute arbitrary PHP code.
CVE-2021-32078
PUBLISHED: 2021-06-17
An Out-of-Bounds Read was discovered in arch/arm/mach-footbridge/personal-pci.c in the Linux kernel through 5.12.11 because of the lack of a check for a value that shouldn't be negative, e.g., access to element -2 of an array, aka CID-298a58e165e4.
CVE-2021-31818
PUBLISHED: 2021-06-17
Affected versions of Octopus Server are prone to an authenticated SQL injection vulnerability in the Events REST API because user supplied data in the API request isn’t parameterised correctly. Exploiting this vulnerability could allow unauthorised access to database tables.
CVE-2021-34825
PUBLISHED: 2021-06-17
Quassel through 0.13.1, when --require-ssl is enabled, launches without SSL or TLS support if a usable X.509 certificate is not found on the local system.
CVE-2021-32944
PUBLISHED: 2021-06-17
A use-after-free issue exists in the DGN file-reading procedure in the Drawings SDK (All versions prior to 2022.4) resulting from the lack of proper validation of user-supplied data. This can result in a memory corruption or arbitrary code execution, allowing attackers to cause a denial-of-service c...