Macof can flood a switch with random mac addresses. A buffer overflow attack is an attack that abuses a type of bug called a buffer overflow, in which a program overwrites memory adjacent to a buffer that should not have been modified intentionally or unintentionally. Buffer overflow attack instructionthe instruction placed right after the function invocation instructioninto the top of the stack, which is the return address region in the stack frame. Network attack and defense university of cambridge. To effectively mitigate buffer overflow vulnerabilities, it is important to understand what buffer overflows are, what dangers they pose to your applications, and what techniques attackers use to successfully exploit these vulnerabilities. Changing arp bindings requires manual intervention. You can find the complete details of cam table overflow attack by going to my below post. When software engineers develop applications,they often set aside specific portions of memoryto contain variable content. What is mac flooding attack and how to prevent mac flooding. The cam overflow attack exploits the fact that a switch is not able to add any new entry to its cam table, and therefore fallbacks into behaving like a hub as it is often described, ill come on this later. You can mitigate cam table overflow attacks in several ways.
Keep in mind that the cam table size can vary by switch model. Practically every worm that has been unleashed in the internet has exploited a bu. Basic, on a x64 linux machine for buffer overflow attack on a c program advanced, on a kali linux machine youll also need a windows machine to perform the attack on for buf. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Overflow a to b mac a sending out multiple packets with various source mac addresses port mac 1a 3x 3y cam. Port security to the rescue when it comes to the cam table overflow attack. Exploiting a buffer overflow allows an attacker to modify portions of the target process address space.
Before we start there is a basic concept in the network field which is switch vs hub. This form of buffer overflow is called a stack smashing attack 14, 30, 28, 35 and constitute a majority of current buffer overflow attacks function pointers. Some of you may recall reading smashing the stack for fun and profit hard to believe that was published in 1996. I have two basic tutorials for that on my blog, hope it might help you. I noticed the cam pdf perl module is built to read the text from a pdf file. This type of attack noticeably impacts network performance, potentially causing applications to drop packets or even crash. Most probably due to a minor bug, it seems that the mac table is. Cam overflow attack and its mitigation prasanna shrestha. The cam table stores information such as mac addresses available on.
Cam table full once the cam table is full, traffic without a cam entry is flooded out every port on that vlan but not traffic with an existing cam entry this will turn a vlan on a switch basically into a hub this attack will also fill the cam tables of adjacent switches btw cisco switches never overwrites an existing entry idle entries are removed. Mar 07, 2016 cam table overflow attack port security ccna security ccnp security. This attack will also fill cam tables of adjacent switches cat6506 enable sho cam count dynamic total matching cam entries 1052 10. The switch enters these into the cam table, and eventually the cam table fills to capacity. Mitigating cam table overflow attacks configuration mode. Cam table overflow attack anthony sequeiras blog home.
The latest example of this is the wannacry ransomware that was big news in 2017 and 2018. Jun 04, 20 buffer overflow attacks have been there for a long time. Cam table overflow attack a switch is a commonly used device in the network,the main difference between switch and a hub, is that switch does not send all packets to all the machines, but will send to the specified target, with the help of the cam table. A computer program may be vulnerable to buffer overflow if it handles incoming data incorrectly. Learn how buffer overflow attacks work and how you can avoid them. A cam table overflow attack works by having a single device or a few devices spoof a large number of mac addresses and send traffic through the switch. Jan 02, 2017 the best and most effective solution is to prevent buffer overflow conditions from happening in the code.
An attacker can use buffer overflow attacks to corrupt the execution stack of a web application. Ca200119 aimed at usoft iis server, port 80, attacker can run arbitrary code on victim machine one goal. The next item pushed into the stack frame by the program is the frame pointer for the previous frame. Apr 25, 2020 a denial of service attacks intent is to deny legitimate users access to a resource such as a network, server etc. There are two types of attacks, denial of service and distributed denial of service. Cam table overflow attack and countermeasure take a walk. Where can i learn how to perform buffer overflow attacks. Cam table overflow attack a switchs content addressable memory cam table contains mac addresses that can be reached, organized by the port where they have been learned, as well as the associated vlan id. Trojan programs, but less is said about the cases of attack of layer 2. Morris worm and buffer overflow well consider the morris worm in more detail when talking about worms and viruses one of the worms propagation techniques was a buffer overflow attack against a vulnerable version of fingerd on vax systems by sending special string to finger daemon, worm caused it to execute code creating a new worm copy.
Cams can provide unusual and irregular motions that may be impossible with the other types of mechanisms. A buffer overflow, or buffer overrun, is a common software coding mistake that an attacker could exploit to gain access to your system. I could discover buffer overflow in a multidimensional array such int y101010. Buffer overflow memory attacks and defenses coursera. Sep 26, 20 mac address overflow attack using backtrack 5 and the way to mitigate it. Mac address overflow attack using backtrack 5 and the way to mitigate it. This attack will also fill cam tables of adjacent switches.
The contentaddressable memory cam table in a switch stores information, such as mac. Therefore, as long as the guessed address points to one of the nops, the attack will be successful. Heapbased, which are difficult to execute and the least common of the two, attack an application by flooding the memory space reserved for a program. Users often provide answers to questions that are criticalto the applications functioningand fill those memory buffers. Tech tips, news, and musings from your friends at almace networks.
Stack overflow public questions and answers teams private questions and answers for your team enterprise private selfhosted questions and answers for your enterprise. Within a very short time, the switchs mac address table is full with fake mac addressport mappings. The cam table overflow attack has been covered multiple times on multiple blogs however, i discovered that no one actually shows you how to capture trafficpasswords off a network suffering from cam overflow and i aim to do just that. This attack is a bit different though because the objective is not to overflow, but to. Background information on cam table overflow attacks and concrete. A cam overflow attack turns a switch into a hub, which. Most of the exploits make use of program bugs, of which the majority are stack overflow vulnerabilities. Defend from hackers using computer networking fundamentals. Among one of the other functions of the cam table is to store the mac address table. The main difference is how the packets are transmitted from one device source a to another destination b. A cam overflow attack occurs when an attacker connects to a single or multiple switch ports and then runs a tool that mimics the existence of thousands of random mac addresses on those switch ports. However,the string manipulation functions will stop when encountering a terminator. Once table is full, traffic without a cam entry floods on the local vlan, but not existing traffic with an existing cam entry.
Instructor buffer overflow attacks also pose a dangerto the security of web applications. The web application security consortium buffer overflow. The attacker sends carefully crafted input to a web application in order to force the web application to execute arbitrary code that allows the attacker to take over the system being attacked. This type of attack is also known as cam table overflow attack. A cam overflow attack turns a switch into a hub, which enables the attacker to eavesdrop on a conversation and perform maninthemiddle attacks.
A common tool that performs cam overflows is macof and is part of the dsniff set of tools. An overflow typically happens when something is filled beyond its capacity. For example when a maximum of 8 bytes as input data is expected, than the amount of data which can be written to the buffer to be limited to 8 bytes at any time. As a result, a cam table overflow attack is by no means a stealth attack, which an attacker might expect to launch without detection. The web application security consortium integer overflows. Hackers all around the world continue to name it as their default tactic due to the huge number of susceptible web applications. How to run a cam table overflow attack in gns3 whitewinterwolf. An integer overflow is the condition that occurs when the result of an arithmetic operation, such as multiplication or addition, exceeds the maximum size of the integer type used to store it. Here is another additional resource from my ccent and ccna exam crams.
Buffer overflows are commonly associated with cbased languages, which do not perform any kind of array bounds checking. Here, we present a typical buffer overflow attack scenario using a simple program. A buffer overflow is a flaw that occurs when more data is written to a block of memory, or buffer, than the buffer is allocated to hold. A denial of service attacks intent is to deny legitimate users access to a resource such as a network, server etc. A denial of service attack can be carried out using syn flooding, ping of death, teardrop, smurf or buffer overflow. So, buffer overrun attacks obviously occur in any program execution that allows input to be written beyond the end of an assigned buffer memory block. Cam overflow attack exploit size limit of cambased switch table send bogus ethernet frames with random source mac addresses each new address will displace an entry in the switch table macof tool. Xxxx first 24 bits manufacture code assigned by ieee xxxx.
Personally, i would never use dynamic port security. Hardcoded passwords make hacking foscam ip cameras much easier june 08, 2017 swati khandelwal security researchers have discovered over a dozen of vulnerabilities in tens of thousands of webconnected cameras that can not be protected just by changing their default credentials. The reason i said partly because sometimes a well written code can be exploited with buffer overflow attacks, as it also depends upon the dedication and intelligence level of the attacker. It still exists today partly because of programmers carelessness while writing a code. Network attack and defense 369 although some of these attacks may have been fixed by the time this book is published, the underlying pattern is fairly constant. The attacker locates an overflowable automatic variable, feeds the program a large string that simultaneously. The simplest and most common form of buffer overflow attack combines an injection technique with an activation record corruption in a single string. This article unleashes memory overflow related security vulnerabilities, in particular, integer overflow resided during source coding inadvertently in software as the number of identification of such bug has been increasing rapidly in the industry and exploited by a hacker for vicious intention.
However, the manufacturing of cams is expensive and the wear effect due to the. With nops, the chance of guessing the correct entry point to the malicious code is signi. Topic 6, common layer 2 attacks flashcards quizlet. A denial of service attack can be carried out using syn flooding, ping of. In a cam table attack, the attacker attempts to flood the switch with bogus mac addresses to exhaust the resources of the cam table thus forcing the switch to forward received on a given interface out all interfaces in the attached vlan. Buffer overflow attack explained with a c program example. Memory on the heap is dynamically allocated by the application at runtime and typically contains program data. Use macof to generate thousands of fake mac addresses to overwhelm a switchs cam table.
A buffer overflow occurring in the heap data area is referred to as a heap overflow and is exploitable in a manner different from that of stackbased overflows. Following images shows a switchs mac address table before and after flooding attack. But the answer that cisco recommends is dynamic port security. Until this gets fixed upstream, it requires a manual modification and. Cam overflow ccnp security secure 642637 quick reference. What is mac flooding attack and how to prevent mac. Hardcoded passwords make hacking foscam ip cameras much. Cam mechanisms are widely used because with them, different types of motion can be possible. Attacker would use a bufferoverflow exploit to take advantage of a program that is waiting on a users input. Also, programmers should be using save functions, test code and fix bugs. In a cam table attack, the attacker attempts to flood the switch with bogus mac addresses to exhaust the resources of the cam table thus forcing the switch to forward received on a. On the left side of the diagram, we have a simple code whose functions contain a dangerous string copy functions and it will copy the data from the area point by str variable to a local variable called buf. An attacker would simply take advantage of any program which is waiting for certain user input and inject surplus data into the buffer.
Switchs mac address table has only a limited amount of memory. Protecting the cam table using port security free ccna workbook. Cbt nuggets trainer keith barker explains how to defend yourself against cam table overflow att. Anybody who can provide suitably crafted user input data may cause such a program to crash or execute arbitrary code. The idea is that the attacker is required to insert these characters in the string used to overflow the buffer to overwrite the canary and remain undetected. Understanding and preventing cam overflow attacks photo by nathan. The cam table can hold a finite number of entries depending on switch model.
Defeating integer overflow attack infosec resources. Basic l2 and l3 security in campus networks cesnet. This fills in the switchs cam table, thus new mac addresses can not be saved, and the switch starts to send all packets to all ports, so it starts to act as a hub, and thus we can monitor all traffic passing through it. Buffer overflow detection is one key element in attack prevention. The switchs cam table will be filled, and all other traffic typically the traffic from legitimate devices will be flooded, causing the switch to become very busy and potentially overloaded. Attacks and defenses for the vulnerabilty of the decade cowan et al.
1139 25 779 304 1374 492 145 491 1168 593 482 46 628 1066 1093 1030 1319 440 1445 730 1473 1002 626 671 629 1475 587 1256 1456 62 758 491 85 550