'handshake'에 해당되는 글 2건

  1. 2014.10.28 새로운 형태의 디도스 공격 발견
  2. 2011.10.27 DoS Attack Tool Targeting SSL Servers
2014. 10. 28. 22:33

새로운 형태의 디도스 공격 발견

‘Tsunami SYN Flood Attack’ 패킷당 1000bytes의 트래픽 유발

일반적인 SYN 패킷 25배 크기로 패킷 데이터양 추가해 공격

http://www.boannews.com/media/view.asp?idx=43654&skind=O


      ▲공격대상별 공격비율

Tsunami SYN-Flood Attack은 주로 ISP나 게임 회사의 데이터센터를 공격했으며 4~5Gbps의 공격이 발생했다. 기존 SYN flood Attack은 패킷당 40~60bytes의 트래픽을 유발하는데 반해 Tsunami SYN-Flood Attack은 패킷당 1000bytes의 트래픽을 유발한다.

[출처]

1. http://itsecuritynews.info/2014/10/12/tsunami-syn-flood-ddos-attack-a-dangerous-trend/

2. http://securityaffairs.co/wordpress/29141/cyber-crime/tsunami-syn-flood-ddos.html

3. http://blog.radware.com/security/2014/10/tsunami-syn-flood-attack/


[용어정리]

·ISP(Internet Service Provider) : 개인이나 기업에 인터넷 접속 서비스, 웹 사이트 구축 등을 제공하는 회사

·TCP 3way handshake : TCP/IP프로토콜을 이용해서 통신을 하는 응용프로그램이 데이터를 전송하기 전에 먼저 정확한 전송을 보장하기 위해 상대방 컴퓨터와 사전에 세션을 수립하는 과정

·봇넷(Botnet) : 스팸메일이나 악성코드 등을 전파하도록 하는 악성코드 봇(Bot)에 감염되어 해커가 마음대로 제어할 수 있는 좀비PC들로 구성된 네트워크



출처 : 보안뉴스


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2011. 10. 27. 13:26

DoS Attack Tool Targeting SSL Servers

A hacker group has released a proof-of-concept tool that exploits how encryption keys can be renegotiated to launch a distributed denial of service attack against Secure Sockets Layer servers.

A tool designed to launch denial of service attacks can bring down Secure Sockets Layer servers using just a laptop computer and a standard DSL connection.

Developed by a German group called The Hacker's Choice, THC-SSL-DOS tool is intended to be a proof-of-concept to disclose "fishy security" in the SSL protocol, the group wrote on The Hacker's Choice blog Oct. 24.

The tool implements the attack by establishing a large number of SSL connections with a given server to eventually consume all of the system resources and making the server unavailable. THC officially released the tool because a version had been leaked accidentally a few months earlier.

The tool exploits a widely known issue with how SSL connections work. A lot of server resources are required to successfully handle SSL "handshakes" at the beginning of a session to establish a secure connection. A client sending enough sessions requests can cause the server to fail. The issue is worsened if the server has the SSL renegotiation feature enabled to handle scenarios that involve processing the client-side certificate.

"It works great if the server supports SSL Renegotiation. It still works if SSL Renegotiation is not supported, but requires some modifications and more bots," the group wrote.

The feature "renegotiates" the key material of an SSL connection, such as in cases where client certificates are used. The Tor Project, which offers users anonymous proxies to hide Web activity, uses renegotiation, as does many smart cards used for Web authentication, Marsh Ray, a developer at PhoneFactor, wrote on the Full Disclosure mailing list.

"A security feature that was supposed to make SSL more secure makes it indeed more vulnerable to this attack," according to THC.

The attack can be mitigated by servers that have SSL acceleration hardware installed, which speeds up the processing of SSL operations.

The tool exists for both Windows and Unix and can be executed with one client on a typical home link. Experts have said in the past that a traditional distributed denial of service attack cannot be launched by home users because servers generally have superior bandwidth than the pipe available to DSL users. THC-SSL-DOS exploits the SSL handshakes to overcome the narrow bandwidth pipe and launch a successful attack without needing a large number of participants.

Attackers can still use the tool successfully on servers where SSL Renegotiation has been disabled. But this approach requires more than a single laptop. Taking on a large server farms that use SSL load balancers required 20 "average size" laptops and a connection with 120kbit/sec of traffic capacity, according to THC.

With threats growing and evolving, companies are trying to protect their environments by deploying Secure-Socket-Layer (SSL) to encrypt connections, Carl Herberger, vice president of security solutions at Radware, told eWEEK. However, a number of vulnerabilities have been exposed in the protocol recently and "most security tools" are not well-equipped to handle the rise of attacks against SSL, Herberger said.

Many hacktivist organizations who are having "less desired" effects with their current attack tools are migrating towards SSL-based attacks as they can "achieve dramatic results" in this space, according to Herberger. "Most companies are sitting ducks as vulnerabilities rise and security defenses are inadequate," he said.

For example, the Low-Orbit Ion Cannon tool favored by hacker groups like Anonymous made it possible for a large number of users on residential network connections to band together to launch an attack successfully and overcome the DSL limitations. However, the group recently released #RefRef, a new tool that was more powerful than LOIC to launch attacks.

"We are hoping that the fishy security in SSL does not go unnoticed. The industry should step in to fix the problem so that citizens are safe and secure again," THC said.

출처 : www.eweek.com

국내 변조 기사 : http://www.zdnet.co.kr/news/news_view.asp?artice_id=20111026101742 


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