Pentesting Network
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This is going to be a brief section about how to find IPs responding from the Internet. In this situation you have some scope of IPs (maybe even several ranges) and you just to find which IPs are responding.
This is the easiest and fastest way to discover if a host is up or not.
You could try to send some ICMP packets and expect responses. The easiest way is just sending an echo request and expect from the response. You can do that using a simple pingor using fpingfor ranges.
You could also use nmap to send other types of ICMP packets (this will avoid filters to common ICMP echo request-response).
You could also perform this step with nmap, but it slower and somewhat nmaphas problems identifying hosts up.
This is just a TCP port discovery useful when you want to focus on discovering HTTP services:
You could also try to check for some UDP port open to decide if you should pay more attention to a host. As UDP services usually don't respond with any data to a regular empty UDP probe packet it is difficult to say if a port is being filtered or open. The easiest way to decide this is to send a packet related to the running service, and as you don't know which service is running, you should try the most probable based on the port number:
Here you can find a nice guide of all the well known Wifi attacks at the time of the writing:
If you are inside the network one of the first things you will want to do is to discover other hosts. Depending on how much noise you can/want to do, different actions could be performed:
You can use these tools to passively discover hosts inside a connected network:
If you ping a subnet broadcast address the ping should be arrive to each host and they could respond to you: ping -b 10.10.5.255
Pinging the network broadcast address you could even find hosts inside other subnets: ping -b 255.255.255.255
Use the -PE, -PP, -PM flags of nmapto perform host discovery sending respectively ICMPv4 echo, timestamp, and subnet mask requests: nmap -PE -PM -PP -sn -vvv -n 10.12.5.0/24
Wake On Lan is used to turn on computers through a network message. The magic packet used to turn on the computer is only a packet where a MAC Dst is provided and then it is repeated 16 times inside the same paket. Then this kind of packets are usually sent in an ethernet 0x0842 or in a UDP packet to port 9. If no [MAC] is provided, the packet is sent to broadcast ethernet (and the broadcast MAC will be the one being repeated).
Once you have discovered all the IPs (external or internal) you want to scan in depth, different actions can be performed.
Open port: SYN --> SYN/ACK --> RST
Closed port: SYN --> RST/ACK
Filtered port: SYN --> [NO RESPONSE]
Filtered port: SYN --> ICMP message
There are 2 options to scan an UDP port:
Send a UDP packet and check for the response ICMP unreachable if the port is closed (in several cases ICMP will be filtered so you won't receive any information inf the port is close or open).
Send a formatted datagrams to elicit a response from a service (e.g., DNS, DHCP, TFTP, and others, as listed in nmap-payloads). If you receive a response, then, the port is open.
Nmap will mix both options using "-sV" (UDP scans are very slow), but notice that UDP scans are slower than TCP scans:
SCTP (Stream Control Transmission Protocol) is designed to be used alongside TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). Its main purpose is to facilitate the transport of telephony data over IP networks, mirroring many of the reliability features found in Signaling System 7 (SS7). SCTP is a core component of the SIGTRAN protocol family, which aims to transport SS7 signals over IP networks.
The support for SCTP is provided by various operating systems, such as IBM AIX, Oracle Solaris, HP-UX, Linux, Cisco IOS, and VxWorks, indicating its broad acceptance and utility in the field of telecommunication and networking.
Two different scans for SCTP are offered by nmap: -sY and -sZ
Misconfigured routers, firewalls, and network devices sometimes respond to network probes using nonpublic source addresses. tcpdump can be utilized to identify packets received from private addresses during testing. Specifically, on Kali Linux, packets can be captured on the eth2 interface, which is accessible from the public Internet. It's important to note that if your setup is behind a NAT or a Firewall, such packets are likely to be filtered out.
Sniffing you can learn details of IP ranges, subnet sizes, MAC addresses, and hostnames by reviewing captured frames and packets. If the network is misconfigured or switching fabric under stress, attackers can capture sensitive material via passive network sniffing.
If a switched Ethernet network is configured properly, you will only see broadcast frames and material destined for your MAC address.
One can, also, capture packets from a remote machine over an SSH session with Wireshark as the GUI in realtime.
Obviously.
ARP Spoofing consist on sending gratuitous ARPResponses to indicate that the IP of a machine has the MAC of our device. Then, the victim will change the ARP table and will contact our machine every time it wants to contact the IP spoofed.
Overflow the switch’s CAM table sending a lot of packets with different source mac address. When the CAM table is full the switch start behaving like a hub (broadcasting all the traffic).
In modern switches this vulnerability has been fixed.
The Dynamic Trunking Protocol (DTP) is designed as a link layer protocol to facilitate an automatic system for trunking, allowing switches to automatically select ports for trunk mode (Trunk) or non-trunk mode. The deployment of DTP is often seen as indicative of suboptimal network design, underscoring the importance of manually configuring trunks only where necessary and ensuring proper documentation.
By default, switch ports are set to operate in Dynamic Auto mode, meaning they are ready to initiate trunking if prompted by a neighboring switch. A security concern arises when a pentester or attacker connects to the switch and sends a DTP Desirable frame, compelling the port to enter trunk mode. This action enables the attacker to enumerate VLANs through STP frame analysis and circumvent VLAN segmentation by setting up virtual interfaces.
Should network vulnerability be identified, the Yersinia tool can be employed to "enable trunking" via the DTP protocol, allowing for the observation of packets from all VLANs.
I would like to point out that Access/Desirable (0x03) indicates that the DTP frame is of the Desirable type, which tells the port to switch to Trunk mode. And 802.1Q/802.1Q (0xa5) indicates the 802.1Q encapsulation type.
By analyzing the STP frames, we learn about the existence of VLAN 30 and VLAN 60.
Once you known VLAN IDs and IPs values, you can configure a virtual interface to attack a specific VLAN. If DHCP is not available, then use ifconfig to set a static IP address.
If an attacker knows the value of the MAC, IP and VLAN ID of the victim host, he could try to double tag a frame with its designated VLAN and the VLAN of the victim and send a packet. As the victim won't be able to connect back with the attacker, so the best option for the attacker is communicate via UDP to protocols that can perform some interesting actions (like SNMP).
Another option for the attacker is to launch a TCP port scan spoofing an IP controlled by the attacker and accessible by the victim (probably through internet). Then, the attacker could sniff in the second host owned by him if it receives some packets from the victim.
To perform this attack you could use scapy: pip install scapy
If you have access to a switch that you are directly connected to, you have the ability to bypass VLAN segmentation within the network. Simply switch the port to trunk mode (otherwise known as trunk), create virtual interfaces with the IDs of the target VLANs, and configure an IP address. You can try requesting the address dynamically (DHCP) or you can configure it statically. It depends on the case.
In certain environments, such as guest wireless networks, port isolation (also known as private VLAN) settings are implemented to prevent clients connected to a wireless access point from directly communicating with each other. However, a technique has been identified that can circumvent these isolation measures. This technique exploits either the lack of network ACLs or their improper configuration, enabling IP packets to be routed through a router to reach another client on the same network.
The attack is executed by creating a packet that carries the IP address of the destination client but with the router's MAC address. This causes the router to mistakenly forward the packet to the target client. This approach is similar to that used in Double Tagging Attacks, where the ability to control a host accessible to the victim is used to exploit the security flaw.
Key Steps of the Attack:
Crafting a Packet: A packet is specially crafted to include the target client's IP address but with the router's MAC address.
Exploiting Router Behavior: The crafted packet is sent up to the router, which, due to the configuration, redirects the packet to the target client, bypassing the isolation provided by private VLAN settings.
VTP (VLAN Trunking Protocol) centralizes VLAN management. It utilizes revision numbers to maintain VLAN database integrity; any modification increments this number. Switches adopt configurations with higher revision numbers, updating their own VLAN databases.
VTP Server: Manages VLANs—creates, deletes, modifies. It broadcasts VTP announcements to domain members.
VTP Client: Receives VTP announcements to synchronize its VLAN database. This role is restricted from local VLAN configuration modifications.
VTP Transparent: Doesn't engage in VTP updates but forwards VTP announcements. Unaffected by VTP attacks, it maintains a constant revision number of zero.
Summary Advertisement: Broadcasted by the VTP server every 300 seconds, carrying essential domain information.
Subset Advertisement: Sent following VLAN configuration changes.
Advertisement Request: Issued by a VTP client to request a Summary Advertisement, typically in response to detecting a higher configuration revision number.
VTP vulnerabilities are exploitable exclusively via trunk ports as VTP announcements circulate solely through them. Post-DTP attack scenarios might pivot towards VTP. Tools like Yersinia can facilitate VTP attacks, aiming to wipe out the VLAN database, effectively disrupting the network.
Note: This discussion pertains to VTP version 1 (VTPv1).
In Yersinia's graphical mode, choose the deleting all VTP vlans option to purge the VLAN database.
If you cannot capture BPDU frames on your interfaces, it is unlikely that you will succeed in an STP attack.
Sending a lot of BPDUs TCP (Topology Change Notification) or Conf (the BPDUs that are sent when the topology is created) the switches are overloaded and stop working correctly.
When a TCP is sent, the CAM table of the switches will be deleted in 15s. Then, if you are sending continuously this kind of packets, the CAM table will be restarted continuously (or every 15segs) and when it is restarted, the switch behaves as a hub
The attacker simulates the behaviour of a switch to become the STP root of the network. Then, more data will pass through him. This is interesting when you are connected to two different switches. This is done by sending BPDUs CONF packets saying that the priority value is less than the actual priority of the actual root switch.
If the attacker is connected to 2 switches he can be the root of the new tree and all the traffic between those switches will pass through him (a MITM attack will be performed).
CISCO Discovery Protocol (CDP) is essential for communication between CISCO devices, allowing them to identify each other and share configuration details.
CDP is configured to broadcast information through all ports, which might lead to a security risk. An attacker, upon connecting to a switch port, could deploy network sniffers like Wireshark, tcpdump, or Yersinia. This action can reveal sensitive data about the network device, including its model and the version of Cisco IOS it runs. The attacker might then target specific vulnerabilities in the identified Cisco IOS version.
A more aggressive approach involves launching a Denial of Service (DoS) attack by overwhelming the switch's memory, pretending to be legitimate CISCO devices. Below is the command sequence for initiating such an attack using Yersinia, a network tool designed for testing:
During this attack, the switch's CPU and CDP neighbor table are heavily burdened, leading to what is often referred to as “network paralysis” due to the excessive resource consumption.
VoIP phones, increasingly integrated with IoT devices, offer functionalities like unlocking doors or controlling thermostats through special phone numbers. However, this integration can pose security risks.
VoIP Hopper offers three modes for the Cisco Discovery Protocol (CDP):
Sniff Mode (-c 0): Analyzes network packets to identify the VLAN ID.
Spoof Mode (-c 1): Generates custom packets mimicking those of an actual VoIP device.
Spoof with Pre-made Packet Mode (-c 2): Sends packets identical to those of a specific Cisco IP phone model.
The preferred mode for speed is the third one. It requires specifying:
The attacker's network interface (-i parameter).
The name of the VoIP device being emulated (-E parameter), adhering to the Cisco naming format (e.g., SEP followed by a MAC address).
In corporate settings, to mimic an existing VoIP device, one might:
Inspect the MAC label on the phone.
Navigate the phone's display settings to view model information.
Connect the VoIP device to a laptop and observe CDP requests using Wireshark.
An example command to execute the tool in the third mode would be:
DoS
Two types of DoS could be performed against DHCP servers. The first one consists on simulate enough fake hosts to use all the possible IP addresses. This attack will work only if you can see the responses of the DHCP server and complete the protocol (Discover (Comp) --> Offer (server) --> Request (Comp) --> ACK (server)). For example, this is not possible in Wifi networks.
Another way to perform a DHCP DoS is to send a DHCP-RELEASE packet using as source code every possible IP. Then, the server will think that everybody has finished using the IP.
You could use the mentioned DoS attacks to force clients to obtain new leases within the environment, and exhaust legitimate servers so that they become unresponsive. So when the legitimate try to reconnect, you can server malicious values mentioned in the next attack.
A rogue DHCP server can be set up using the DHCP script located at /usr/share/responder/DHCP.py. This is useful for network attacks, like capturing HTTP traffic and credentials, by redirecting traffic to a malicious server. However, setting a rogue gateway is less effective since it only allows capturing outbound traffic from the client, missing the responses from the real gateway. Instead, setting up a rogue DNS or WPAD server is recommended for a more effective attack.
Below are the command options for configuring the rogue DHCP server:
Our IP Address (Gateway Advertisement): Use -i 10.0.0.100 to advertise your machine's IP as the gateway.
Local DNS Domain Name: Optionally, use -d example.org to set a local DNS domain name.
Original Router/Gateway IP: Use -r 10.0.0.1 to specify the IP address of the legitimate router or gateway.
Primary DNS Server IP: Use -p 10.0.0.100 to set the IP address of the rogue DNS server you control.
Secondary DNS Server IP: Optionally, use -s 10.0.0.1 to set a secondary DNS server IP.
Netmask of Local Network: Use -n 255.255.255.0 to define the netmask for the local network.
Interface for DHCP Traffic: Use -I eth1 to listen for DHCP traffic on a specific network interface.
WPAD Configuration Address: Use -w “http://10.0.0.100/wpad.dat” to set the address for WPAD configuration, assisting in web traffic interception.
Spoof Default Gateway IP: Include -S to spoof the default gateway IP address.
Respond to All DHCP Requests: Include -R to make the server respond to all DHCP requests, but be aware that this is noisy and can be detected.
By correctly using these options, a rogue DHCP server can be established to intercept network traffic effectively.
Here are some of the attack tactics that can be used against 802.1X implementations:
Active brute-force password grinding via EAP
Attacking the RADIUS server with malformed EAP content **(exploits)
EAP message capture and offline password cracking (EAP-MD5 and PEAP)
Forcing EAP-MD5 authentication to bypass TLS certificate validation
Injecting malicious network traffic upon authenticating using a hub or similar
If the attacker if between the victim and the authentication server, he could try to degrade (if necessary) the authentication protocol to EAP-MD5 and capture the authentication attempt. Then, he could brute-force this using:
FHRP (First Hop Redundancy Protocol) is a class of network protocols designed to create a hot redundant routing system. With FHRP, physical routers can be combined into a single logical device, which increases fault tolerance and helps distribute the load.
Cisco Systems engineers have developed two FHRP protocols, GLBP and HSRP.
Three versions of the Routing Information Protocol (RIP) are known to exist: RIP, RIPv2, and RIPng. Datagrams are sent to peers via port 520 using UDP by RIP and RIPv2, whereas datagrams are broadcasted to UDP port 521 via IPv6 multicast by RIPng. Support for MD5 authentication was introduced by RIPv2. On the other hand, native authentication is not incorporated by RIPng; instead, reliance is placed on optional IPsec AH and ESP headers within IPv6.
RIP and RIPv2: Communication is done through UDP datagrams on port 520.
RIPng: Utilizes UDP port 521 for broadcasting datagrams via IPv6 multicast.
Note that RIPv2 supports MD5 authentication while RIPng does not include native authentication, relying on IPsec AH and ESP headers in IPv6.
EIGRP (Enhanced Interior Gateway Routing Protocol) is a dynamic routing protocol. It is a distance-vector protocol. If there is no authentication and configuration of passive interfaces, an intruder can interfere with EIGRP routing and cause routing tables poisoning. Moreover, EIGRP network (in other words, autonomous system) is flat and has no segmentation into any zones. If an attacker injects a route, it is likely that this route will spread throughout the autonomous EIGRP system.
To attack a EIGRP system requires establishing a neighbourhood with a legitimate EIGRP router, which opens up a lot of possibilities, from basic reconnaissance to various injections.
In Open Shortest Path First (OSPF) protocol MD5 authentication is commonly employed to ensure secure communication between routers. However, this security measure can be compromised using tools like Loki and John the Ripper. These tools are capable of capturing and cracking MD5 hashes, exposing the authentication key. Once this key is obtained, it can be used to introduce new routing information. To configure the route parameters and establish the compromised key, the Injection and Connection tabs are utilized, respectively.
Capturing and Cracking MD5 Hashes: Tools such as Loki and John the Ripper are used for this purpose.
Configuring Route Parameters: This is done through the Injection tab.
Setting the Compromised Key: The key is configured under the Connection tab.
The attacker configures all the network parameters (GW, IP, DNS) of the new member of the network sending fake DHCP responses.
ICMP Redirect consist on sending an ICMP packet type 1 code 5 that indicates that the attacker is the best way to reach an IP. Then, when the victim wants to contact the IP, it will send the packet through the attacker.
The attacker will resolve some (or all) the domains that the victim ask for.
Configure own DNS with dnsmasq
Multiple routes to systems and networks often exist. Upon building a list of MAC addresses within the local network, use gateway-finder.py to identify hosts that support IPv4 forwarding.
For local host resolution when DNS lookups are unsuccessful, Microsoft systems rely on Link-Local Multicast Name Resolution (LLMNR) and the NetBIOS Name Service (NBT-NS). Similarly, Apple Bonjour and Linux zero-configuration implementations utilize Multicast DNS (mDNS) for discovering systems within a network. Due to the unauthenticated nature of these protocols and their operation over UDP, broadcasting messages, they can be exploited by attackers aiming to redirect users to malicious services.
Browsers commonly employ the Web Proxy Auto-Discovery (WPAD) protocol to automatically acquire proxy settings. This involves fetching configuration details from a server, specifically through a URL such as "http://wpad.example.org/wpad.dat". The discovery of this server by the clients can happen through various mechanisms:
Through DHCP, where the discovery is facilitated by utilizing a special code 252 entry.
By DNS, which involves searching for a hostname labeled wpad within the local domain.
Via Microsoft LLMNR and NBT-NS, which are fallback mechanisms used in cases where DNS lookups do not succeed.
This attack is very similar to ARP Spoofing but in the IPv6 world. You can get the victim think that the IPv6 of the GW has the MAC of the attacker.
Some OS configure by default the gateway from the RA packets sent in the network. To declare the attacker as IPv6 router you can use:
By default some OS try to configure the DNS reading a DHCPv6 packet in the network. Then, an attacker could send a DHCPv6 packet to configure himself as DNS. The DHCP also provides an IPv6 to the victim.
Basically what this attack does is, in case the user try to access a HTTP page that is redirecting to the HTTPS version. sslStrip will maintain a HTTP connection with the client and a HTTPS connection with the server so it ill be able to sniff the connection in plain text.
The difference between sslStrip+ and dns2proxy against sslStrip is that they will redirect for example www.facebook.com to wwww.facebook.com (note the extra "w") and will set the address of this domain as the attacker IP. This way, the client will connect to wwww.facebook.com (the attacker) but behind the scenes sslstrip+ will maintain the real connection via https with www.facebook.com.
TODO: easy-creds, evilgrade, metasploit, factory
Some times, if the client checks that the CA is a valid one, you could serve a certificate of other hostname signed by a CA. Another interesting test, is to serve a certificate of the requested hostname but self-signed.
Other things to test is to try to sign the certificate with a valid certificate that it is not a valid CA. Or to use the valid public key, force to use an algorithm as diffie hellman (one that do not need to decrypt anything with the real private key) and when the client request a probe of the real private key (like a hash) send a fake probe and expect that the client does not check this.
Take into account that when a UDP packet is sent to a device that do not have the requested port an ICMP (Port Unreachable) is sent.
ARP packets are used to discover wich IPs are being used inside the network. The PC has to send a request for each possible IP address and only the ones that are being used will respond.
Bettercap send a MDNS request (each X ms) asking for _services_.dns-sd._udp.local the machine that see this paket usually answer this request. Then, it only searchs for machine answering to "services".
Tools
Avahi-browser (--all)
Bettercap (net.probe.mdns)
Responder
Bettercap broadcast packets to the port 137/UDP asking for the name "CKAAAAAAAAAAAAAAAAAAAAAAAAAAA".
Bettercap broadcast SSDP packets searching for all kind of services (UDP Port 1900).
Bettercap broadcast WSD packets searching for services (UDP Port 3702).
Network Security Assessment: Know Your Network (3rd edition)
Practical IoT Hacking: The Definitive Guide to Attacking the Internet of Things. By Fotios Chantzis, Ioannis Stais, Paulino Calderon, Evangelos Deirmentzoglou, Beau Wood
It's very common to find that all kind of ICMP packets are being filtered. Then, all you can do to check if a host is up is try to find open ports. Each host has 65535 ports, so, if you have a "big" scope you cannot test if each port of each host is open or not, that will take too much time. Then, what you need is a fast port scanner () and a list of the ports more used:
The nmap line proposed before will test the top 1000 UDP ports in every host inside the /24 range but even only this will take >20min. If need fastest results you can use : ./udp-proto-scanner.pl 199.66.11.53/24 This will send these UDP probes to their expected port (for a /24 range this will just take 1 min): DNSStatusRequest, DNSVersionBindReq, NBTStat, NTPRequest, RPCCheck, SNMPv3GetRequest, chargen, citrix, daytime, db2, echo, gtpv1, ike,ms-sql, ms-sql-slam, netop, ntp, rpc, snmp-public, systat, tftp, time, xdmcp.
Note that the techniques commented in (TCP/HTTP/UDP/SCTP Port Discovery) can be also applied here. But, as you are in the same network as the other hosts, you can do more things:
Note that the techniques commented in Discovering hosts from the outside () can be also applied here. But, as you are in the same network as the other hosts, you can do more things:
You can use tools like to parse credentials from a pcap or a live interface.
The presence of DTP in many switches by default can be exploited by adversaries to mimic a switch's behavior, thereby gaining access to traffic across all VLANs. The script is utilized to monitor an interface, revealing whether a switch is in Default, Trunk, Dynamic, Auto, or Access mode—the latter being the only configuration immune to VLAN hopping attacks. This tool assesses the switch's vulnerability status.
To enumerate the VLANs it's also possible to generate the DTP Desirable frame with the script . Do not interrupt the script under any circumstances. It injects DTP Desirable every three seconds. The dynamically created trunk channels on the switch only live for five minutes. After five minutes, the trunk falls off.
The discussed attack of Dynamic Trunking and creating virtual interfaces an discovering hosts inside other VLANs are automatically performed by the tool:
You could also use . Be sure to install it with scapy/contrib package.
The tool is designed to emulate a VoIP phone in various environments (Cisco, Avaya, Nortel, Alcatel-Lucent). It discovers the voice network's VLAN ID using protocols like CDP, DHCP, LLDP-MED, and 802.1Q ARP.
A more automatic way of doing this is using the tool
allows you to implement a virtual router that supports BGP, OSPF, EIGRP, RIP and other protocols. All you need to do is deploy it on your attacker’s system and you can actually pretend to be a legitimate router in the routing domain.
has capabilities for intercepting EIGRP (Enhanced Interior Gateway Routing Protocol) broadcasts. It also allows for the injection of packets, which can be utilized to alter routing configurations.
: Tool to scan network traffic and find vulnerabilities
You can find some more information about network attacks .
Check the .
You can impersonate services that are searched by hosts using Responder to send fake responses. Read here more information about .
The tool Responder takes advantage of this protocol by acting as a malicious WPAD server. It uses DHCP, DNS, LLMNR, and NBT-NS to mislead clients into connecting to it. To dive deeper into how services can be impersonated using Responder .
You can offer different services in the network to try to trick a user to enter some plain-text credentials. More information about this attack in .
More info .
The goal of this technique is to avoid HSTS because wwww.facebook.com won't be saved in the cache of the browser, so the browser will be tricked to perform facebook authentication in HTTP. Note that in order to perform this attack the victim has to try to access initially to and not https. This can be done modifying the links inside an http page.
More info , and .
sslStrip or sslStrip+ doesn;t work anymore. This is because there are HSTS rules presaved in the browsers, so even if it's the first time that a user access an "important" domain he will access it via HTTPS. Also, notice that the presaved rules and other generated rules can use the flag so the wwww.facebook.com example from before won't work anymore as facebook.com uses HSTS with includeSubdomains.
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