Private vlans are a layer 2 feature that is supposed to restrict traffic to layer 2. Which feature on a switch makes it vulnerable to vlan. Communication between vlans is only possible by a router, such as a layer 3 switch or a router configured with subinterfaces routeronastick or multiple lan connections. So do layer 2 network attacks that typically work on physical devices apply to their virtualized counterparts. The short version is that all the following things will open you up to a vlan hopping attack. In figure 3 below, there are three vlans, 5, 10 and 15. In a basic vlan hopping attack, the attacker takes advantage of the automatic trunking port feature enabled by default on most switch ports. Mitigating a vlan hopping attack can be done by disabling dynamic trunking protocol dtp and by setting the native vlan of trunk links to a vlan not in use. Vlan hopping is a security threat, a method of attacking networked resources on a virtual lan vlan. By altering the vlan id on packets encapsulated for trunking, an attacking device can send or receive packets on various vlans, bypassing layer 3 security measures.
Vlan hopping attacks are hard to discover because the attacker is. Basic vlan hopping attack an end station can spoof as a switch with isl or 802. Hacking vlan switched networks i wanted to post this for those rare hackers and network admins out there trying to find vlan info. The device with mac address aabbcc has changed locations to port2. When asked to elaborate they will respond with vague, handwaving arguments along the lines that it is possible to get traffic to hop. The switch receives the frame and recognizes that this packet is coming from a device of vlan 10. A vlan hopping attack can occur in either of two ways.
This means we can modify our switchs vlan configuration and sniff any vlans traffic. The switch spoofing is a type of vlan hopping attack, a switch interface which is connected to an end device a computer or a printer are normally in access mode and that end device will have access to its own vlan. The confusion stems from the fact that different sources including the official certification guide form cisco press often only address one of the attack types. Ethernet switch attack resilience varies widely from vendor to. With these security vulnerabilities present it might.
In this article we will mitigate vlan hopping by switch spoofing in the way that we will disable trunking on the ports who do not have to become trunk ports. There seems to be a certain amount of fud around about the security of vlans for trafficsegregation. Understanding vlan hopping attacks it tips for systems and. In both of these scenarios vlan hopping is a possibility which must be taken into consideration when configuring the lan. Vlan hopping attack can be possible by two different approaches, switch spoofing or double tagging. Vlan hopping, arp poisoning, and maninthe middle attacks in. Vlan hopping can be accomplished by switch spoofing or double tagging. Dtp vulnerability attack and vlan hopping attack technote. In my previous article on vlans, the anatomy of a vlan published in redscans july 20 newsletter, i explained how trunks on switches carry traffic for all vlans. Mac address spoofing attack 20 mac address spoofing attack mac address. So, the switch removes the vlan 10 identifier, leaving only one entry. The majority of layer 2 data link layer attacks exploit the inability of a switch to track an attacker, because the switch has no inherent mechanism to detect that an attack is occurring. Skills covered in this course network administration security it cisco routers.
Configuration on a cisco switch is shown in which the native vlan has been set to an unused vlan. If a cisco switch enabled dtp protocol on an interface, attacker can use their laptop send the dynamic desirable frame to the interface, there for, the target interface will become trunking port. Buffer overflow, cross site scripting and sql injection have had their share of the spotlight, i have recently decided to give more attention to layer two. Some cisco switches ports default to auto mode for trunking. Even though vlans are rarer these daysthere isnt much vlan info on the net in terms of specifics and i had to learn all about it because i needed to log in to a switch that was on a different vlan. Which type of vlanhopping attack may be prevented by designating an unused vlan as the native vlan. Attack used to gain unauthorized access to another virtual lan on a packet switched network attacker sends frames from one vlan to another that would otherwise be inaccessible two methods. Aabbcc attacker port 1 port 2 aabbcc 1 2 i have changed the mac address on my computer to match the server. A vlan is a local area network with a definition that maps devices on some other basis than geographic. Vlan hopping is used to attack a network by sending packets to a port which is generally not accessible.
Vlan hopping, arp poisoning and maninthemiddle attacks in virtualized environments. Frogger the vlan hopper common exploits penetration. There are two different methods to accomplish this. You might, for testing purposes, add the command switchport trunk native vlan 20 to fa01. To then eliminate the threat of vlan hopping the native vlan should not be used where clients connect to the switch. Vlan hopping attacks are mainly conducted in the dynamic trunkingprotocol and, in some cases. A pc will claim to establish a trunk link between itself and the switch and gain all the vlan informations. Mitigate vlan hopping attack get rid of layer 2 attacks. Vlan hopping vlan hopping is one of the primary vlan based attacks used by hackers to infiltrate network security. Another option in newer switches is to enable tagging of the native. To be able to do a vlan hopping attack the attacker would have to unplug the access point and then plug their machine into that same port.
Switch spoofing cisco proprietary double tagging exploitation of 802. Having any unauthenticated dynamic trunking protocol on the switch connected to the vmware server. Allowing any ethertypes other than 0x0800 and 0x0806 on your internet vlan. Vlan hopping, arp poisoning and maninthemiddle attacks in virtualized environments conference paper pdf available august 2016 with 1,377 reads how we measure reads. Disable trunk negotiation on all ports connecting to workstations. Is when a station is able to access vlan other than its own. Jul 18, 2018 information security services, news, files, tools, exploits, advisories and whitepapers. Firstly it is not a tool so to speak, it is simply a bash script i put together that automates the process of vlan enumerating and hopping end to end with interactive menus etc. What is vlan hopping attack switch spoofing and double tagging vlan hopping is a type of network attack where an attacker who is connected to an access port which is attached to a particular vlan can gain access to network traffic from other vlan s. Information security services, news, files, tools, exploits, advisories and whitepapers.
An attacker can craft and send positioned frames on one access vlan with spoofed 802. When you change the address on your laptop are you doing it on a sub interface like directed, tagging your nic traffic vlan 20. The attacker can connect an unauthorized cisco switch to a company switch port. It assumes the frame belongs to the stated vlan on this tag vlan 2 and forwards to all ports configured for vlan 2. Vlan 40, which forwards the frame to the next switch. Allowing any ethertypes other than 0x0800 and 0x0806 on. Which feature on a switch makes it vulnerable to vlan hopping. Even though vlans are rarer these daysthere isnt much vlan info on the net in terms of specifics and i had to learn all about it because i needed to log in to a. Due to the nature of this attack, it is strictly one way. A vlan trunk has been configured to allow the two sites to communicate. Here is a little script i made that automates vlan enumeration and hopping. Switch spoofing is a virtual lan vlan hopping attack that is characterized by using dynamic trunking protocol dtp to negotiate a trunk link with a switch port in order to capture all traffic that is allowed on the trunk. This type of attack takes advantage of the way that hardware on most switches operates.
The target then receives the packet sent by the attacker. Review some attacks that can occur in the data link layer or layer 2, such as stp attack, arp and mac spoofing, vlan hopping attacks, and dhcp attacks. Some members of the informationsecurity community will tell you that vlans are not secure and cannot safely be used for trafficsegregation. Forge vlan, priority or aggregation tags spoof pause flow control frames gig only. To help prevent a vlan hopping attack using double tagging, do not use the native vlan to send user traffic. We will start by taking a quick look at a normal switched network, pointing out its main characteristics and then move on to vlans. If that works, then youre not tagging your laptop traffic vlan 20. Please also note that this attack may not work on new switches. Both of the above mitigation options will prevent the vlan hopping attack, but be aware that a third option.
It is understood that the clients or end systems must not and will not send tagged data frames if they are on access ports because they dont. Dec 11, 2017 switch spoofing is a virtual lan vlan hopping attack that is characterized by using dynamic trunking protocol dtp to negotiate a trunk link with a switch port in order to capture all traffic that is allowed on the trunk. You can do this by creating a vlan that does not have any ports added. It is understood that the clients or end systems must not and will not send tagged data frames if they are on access.
The vlan attack, or how to become the vlans master blackhat eu 2005 ieee 802. A private vlan attack uses the expected behavior of a private vlan against the vlan itself. Private vlans allow traffic to be further segmented at layer 2, limiting the size of your broadcast domain. Pdf vlan hopping, arp poisoning and maninthemiddle.
Vlan hopping from occurring with newer models my simply configuring the port as access ports. Vlan hopping virtual local area network hopping is a method of attacking a network by sending packets to a port that is not normally accessible from a given end system. This unused vlan is only for the native vlan assignment. Based on 10, the hardenings of the switches succeed to protect vlans against the attacks, but this has rapidly increased the work of the administrator. Native vlan vlan 10 vlan 20 vlan 20 vlan 10 trunk with. The second countermeasure is to assign the native vlan on all switch trunks to an unused vlan. What are the primary attack methods of vlan hopping. Any unused ports should be disabled and set as access mode ports by default. Which two layer 2 security best practices would help prevent vlan hopping attacks. The basic concept behind all vlan hopping attacks is where a user can gain access to a vlan not assigned to the switch port to which the user connects.
Learn vocabulary, terms, and more with flashcards, games, and other study tools. I often receive questions from ccnp candidates around what preventative measures can mitigate a vlan hopping attack. Understanding, preventing, and defending against layer 2. A vlan hopping attack enables traffic from one vlan to be seen by another vlan without routing. Native vlan vlan 10 vlan 20 an end station can spoof as a switch with isl or 802. Understanding, preventing, and defending against layer 2 attacks. Oct 09, 2018 a specific type of vlan threat is a vlan hopping attack. Even different language is frequently used to describe the same attack vector.
Traffic flooding is constrained within the vlan of origin, and therefore no vlan hopping is permitted. Ensure that the native vlan is used for management traffic. The basic concept behind all vlan hopping attacks is for an attacking host on a vlan to gain access to traffic on other vlans that would normally not be accessible. In a switch spoofing attack, the attacking system is configured to act like a switch with a trunk port. Understanding vlan hopping attacks it tips for systems. A trunk port is a port for communication between switches, and for transporting multiple. When you are in a situation where you need to configure and set up the security of vlan trunks, also consider the potential for an exploit called vlan hopping an attacker can craft and send positioned frames on one access vlan with spoofed 802. Route process ddos attack note, other types of local attacks may target routers. Vlan hopping virtual local area network hopping is a method of attacking a. Valter popeskic configuration, security layer 2 no comments. To help start clearing things up we will define the vlan concept not only through words, but through the use of our cool diagrams and at the same time, compare vlans to our standard flat switched network. Def con 24 vlan hopping, arp poisoning and maninthe. What is vlan hopping attack switch spoofing and double.
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