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Linux Advisory Watch: December 30th 2005 Print E-mail
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Source: Contributors - Posted by Benjamin D. Thomas   
Linux Advisory Watch This week, advisories were released for phpbb2, ketm, tkdiff, dhis-tools-dns, Mantis, NDB, rssh, OpenMotif, scponly, msec, fetchmail, cpio, php-mbstring, and libgphoto. The distributors include Debian, Gentoo, and Mandriva.

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IPv6 approach for TCP SYN Flood attack over VoIP, Part II
By: Suhas Desai

There are several general categories of DoS attacks. Some groups divide attacks into three classes: bandwidth attacks, protocol attacks, and logic attacks. Following are brief descriptions of some common types of DoS attacks.

3.1 Bandwidth attacks

Bandwidth attacks are relatively straightforward attempts to consume resources, such as network bandwidth or equipment throughput. High-data-volume attacks can consume all available bandwidth between an ISP and your site. The link fills up, and legitimate traffic slows down. Timeouts may occur, causing retransmission, generating even more traffic. An attacker can consume bandwidth by transmitting any traffic at all on your network connection. A basic flood attack might use UDP or ICMP packets to simply consume all available bandwidth. For that matter, an attack could consist of TCP or raw IP packets, as long as the traffic is routed to your network.

A simple bandwidth-consumption attack can exploit the throughput limits of servers or network equipment by focusing on high packet rates—sending large numbers of small packets. High-packet-rate attacks typically overwhelm network equipment before the traffic reaches the limit of available bandwidth. Routers, servers, and firewalls all have constraints on input-output processing, interrupt processing, CPU, and memory resources. Network equipment that reads packet headers to properly route traffic becomes stressed handling the high packet rate (pps), not the volume of the data (Mbps). In practice, denial of service is often accomplished by high packet rates, not by sheer traffic volume.

3.2 Protocol Attacks

The basic flood attack can be further refined to take advantage of the inherent design of common network protocols. These attacks do not directly exploit weaknesses in TCP/IP stacks or network applications but, instead, use the expected behavior of protocols such as TCP, UDP, and ICMP to the attacker's advantage. Examples of protocol attacks include the following:

SYN flood is an asymmetric resource starvation attack in which the attacker floods the victim with TCP SYN packets and the victim allocates resources to accept perceived incoming connections. As mentioned above, the proposed Host Identity Payload and Protocol (HIP) are designed to mitigate the effects of a SYN flood attack. Another technique, SYN Cookies is implemented in some TCP/IP stacks.

Smurf is an asymmetric reflector attack that targets a vulnerable network broadcast address with ICMP ECHO REQUEST packets and spoofs the source of the victim.

Fraggle is a variant of smurf that sends UDP packets to echo or chargen ports on broadcast addresses and spoofs the source of the victim.

3.3 Software Vulnerability Attacks

Unlike flooding and protocol attacks, which seek to consume network or state resources, logic attacks exploit vulnerabilities in network software, such as a web server, or the underlying TCP/IP stack. Some vulnerability by crafting even a single malformed packet.

Teardrop (bonk, boink) exploits TCP/IP IP stacks that do not properly handle overlapping IP fragments.

Land crafts IP packets with the source address and port set to be the same as the destination address and port.

Ping of death sends a single large ICMP ECHO REQUEST packet to the target.

Naptha is a resource-starvation attack that exploits vulnerable TCP/IP stacks using crafted TCP packets. There are many variations on these common types of attacks and many varieties of attack tools to implement them.

Read Article: Feature Extras:

Linux File & Directory Permissions Mistakes - One common mistake Linux administrators make is having file and directory permissions that are far too liberal and allow access beyond that which is needed for proper system operations. A full explanation of unix file permissions is beyond the scope of this article, so I'll assume you are familiar with the usage of such tools as chmod, chown, and chgrp. If you'd like a refresher, one is available right here on

Introduction: Buffer Overflow Vulnerabilities - Buffer overflows are a leading type of security vulnerability. This paper explains what a buffer overflow is, how it can be exploited, and what countermeasures can be taken to prevent the use of buffer overflow vulnerabilities.

Getting to Know Linux Security: File Permissions - Welcome to the first tutorial in the 'Getting to Know Linux Security' series. The topic explored is Linux file permissions. It offers an easy to follow explanation of how to read permissions, and how to set them using chmod. This guide is intended for users new to Linux security, therefore very simple. If the feedback is good, I'll consider creating more complex guides for advanced users. Please let us know what you think and how these can be improved.


Take advantage of our Linux Security discussion list! This mailing list is for general security-related questions and comments. To subscribe send an e-mail to with "subscribe" as the subject.

Thank you for reading the weekly security newsletter. The purpose of this document is to provide our readers with a quick summary of each week's most relevant Linux security headline.

  Debian: New phpbb2 packages fix several vulnerabilities
  22nd, December, 2005

Updated package.
  Debian: New ketm packages fix privilege escalation
  23rd, December, 2005

Updated package.
  Debian: New ketm packages fix privilege escalation
  23rd, December, 2005

Updated package.
  Debian: New tkdiff packages fix insecure temporary file creation
  27th, December, 2005

Updated package.
  Debian: New dhis-tools-dns packages fix insecure temporary file creation
  27th, December, 2005

Updated package.
  Debian: New tkdiff packages fix insecure temporary file creation
  29th, December, 2005

Updated package.
  Gentoo: Mantis Multiple vulnerabilities
  22nd, December, 2005

Mantis is affected by multiple vulnerabilities ranging from file upload and SQL injection to cross-site scripting and HTTP response splitting.
  Gentoo: Dropbear Privilege escalation
  23rd, December, 2005

A buffer overflow in Dropbear could allow authenticated users to execute arbitrary code as the root user.
  Gentoo: NBD Tools Buffer overflow in NBD server
  23rd, December, 2005

The NBD server is vulnerable to a buffer overflow that may result in the execution of arbitrary code.
  Gentoo: rssh Privilege escalation
  27th, December, 2005

Local users could gain root privileges by chrooting into arbitrary directories.
  Gentoo: OpenMotif, AMD64 x86 emulation X libraries Buffer
  28th, December, 2005

Two buffer overflows have been discovered in libUil, part of the OpenMotif toolkit, that can potentially lead to the execution of arbitrary code.
  Gentoo: scponly Multiple privilege escalation issues
  29th, December, 2005

Local users can exploit an scponly flaw to gain root privileges, and scponly restricted users can use another vulnerability to evade shell restrictions.
  Mandriva: Updated msec packages fixes various bugs
  22nd, December, 2005

Bugs in the msec package have been corrected: msec wasn't properly parsing the output on security checks to check ownership of files, reporting files as unowned when they were in fact properly owned by a valid user.
  Mandriva: Updated fetchmail packages fix vulnerability
  23rd, December, 2005

Fetchmail before 6.3.1 and before, when configured for multidrop mode, allows remote attackers to cause a DoS (application crash) by sending messages without headers from upstream mail servers.
  Mandriva: Updated cpio packages fix buffer overflow on x86_64
  23rd, December, 2005

A buffer overflow in cpio 2.6 on 64-bit platforms could allow a local user to create a DoS (crash) and possibly execute arbitrary code when creating a cpio archive with a file whose size is represented by more than 8 digits.
  Mandriva: Updated digikamimageplugins packages fix showfoto crash issue.
  26th, December, 2005

A previous update of DigiKam (MDKA-2005:059) bumped the version to 0.8.0. After this update, Narfi Stefansson reported that showfoto, from digikamimageplugins was crashing when trying to use "Free Rotation". This update bumps digikamimageplugins to version 0.8.0 also.
  Mandriva: Updated php/php-mbstring packages fix mail injection vulnerability
  27th, December, 2005

A CRLF injection vulnerability in the mb_send_mail function in PHP before 5.1.0 might allow remote attackers to inject arbitrary e-mail headers via line feeds (LF) in the "To" address argument, when using sendmail as the MTA (mail transfer agent).
  Mandriva: Updated libgphoto packages fixes issue with some cameras
  29th, December, 2005

The hotplug usermap has been restored for this package because it is used by HAL to correctly detect digital cameras which are not using USB Mass storage (for instance, all Canon digital cameras, as well as some Nikon ones and all PTP cameras). This should allow gnome-volume-manager to automatically popup a "Do you want to import photos?" dialog when the camera is plugged in.

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