Questions tagged [icmp]

Abreviation of Internet Control Message Protocol. The protocol allows for the return propagation of error messages related to IP packets. ICMP is critical to basic network tools like ping and traceroute.

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In what situations / with what nodes should a node ping / not ping?

I was recently looking at a network in which the client-machines that accessed a webservice endpoint, but which could not ping the webservice endpoint. And there are other machines that can ping the ...
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Security auditing - disabling IP forwarding and ICMP packets redirects

I've recently started working as a security auditor and my mentor gave me some homework to write an Ubuntu security audit script so that I'll get to learn to use batch scripting and understand ...
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ICMP Packet collection fails with airodump-ng

I have 3 machines (A,B, and C) connected to the same wireless network. I can ping A to B and vice versa. Machine C is set to monitor mode using airmon-ng and airodump-ng commands. When I try to ...
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Why Does Windows Server Block ICMP By Default? [duplicate]

I am conducting a OpenVAS vulnerability scan on a Windows Server 2012 box and it came back empty. It turns out that the scanner checks to see if the host is alive by sending it a ping request--if it ...
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UDP vs ICMP flood

How can we measure the efficiency of the flood technique? Will it be by the number of bots required for flooding the link? In case of UDP and ICMP, which one would be more efficient and why?
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Is ping of death attack specific to ICMP or could it also happen with other transport protocols?

A Ping of Death attack is a denial-of-service (DoS) attack, in which the attacker aims to disrupt a targeted machine by sending a packet larger than the maximum allowable size, causing the target ...
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Investigate compromised Linux server

I'm investigating a server that pings throughout the day to random IPs on the internet. I set up IPtables to log and drop (INPUT & OUTPUT) packets but I still see icmp traffic on the network ...
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Spoofing an IP/MAC address to avoid ICMP Destination Unreachable being sent back [duplicate]

As far as I understand UDP flooding the idea is to send UDP packets across all ports from e.g. Alice to Bob, and get Bob's machine to check who listens to certain ports and generate many ICMP ...
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Continuous ping on google's servers

Using Wireshark, I recently discovered that my computer (running on Windows 10) is sending ping requests to Google's servers. According to wireshark, my computer is sending ICMP requests and receive ...
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Smurf Attack confusion

I have a question regarding the Smurf Attack described in the following CISCO article: http://www.cisco.com/c/en/us/about/security-center/guide-ddos-defense.html#9 In a smurf attack, an attacker ...
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How to prevent ICMP redirection produced by a man-in-the-middle

How can I prevent my route to be redirected with redirecting ICMP packets from a man-in-the-middle? I am specifically looking to avoid someone using ettercap with the -M icmp option. From man ...
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NMAP discovery scan reporting host offline, pinging the same host gets ICMP responses

I ran an nmap -sn scan on a host, and nmap reported the host as down. I then pinged the same host with ping and got ICMP responses. I'm confused, because I was sure that -sn among other things, did an ...
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Risks of pinging/resolving malicious sites?

If I do ping malicioussite.com or nslookup malicioussite.com, is there any risk for me? Will the people behind the malicious site know I'm looking them up? I'd like to make a program to use an IP ...
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What happens when a firewall blocks a traceroute?

I am trying to find out what happens when you try to access a site using traceroute command, but I cannot find any site that is actually blocking me. Anyway, I wanted to ask what happens when a ...
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Is pinging a website essentially the same as visiting the website through a browser?

I was looking at the domain information of a website (poaulpos.net) on who.is that Chrome connects to whenever I visit a specific an old Tech Times article about Thunderstrike 2, a Mac firmware attack ...
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script for analysis of tcpdump log file

I'm trying to get the following metrics from my tcpdump log file: (1) one-way delay, (2) request/response delay, (3) packet loss, (4) overall transaction duration and (5) delay variation (jitter). ...
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Can ICMP Redirects still be used to redirect traffic in a LAN?

I tried just tried to migrate a MITM attack using hping3 with ICMP Redirects in my testlab. hping3 -I eth0 -C 5 -K 1 -a 192.168.2.1 --icmp-ipdst 192.168.2.15 --icmp-gw 192.168.2.100 --icmp-ipsrc 192....
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Reliability of scanning tools on icmp timestamp responses

A security auditor has done a vulnerability scan of our network and found that one of our server has returned an TCP timestamp response such that the scanner (Nmap) is able to guess the uptime of the ...
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When should I drop a packet with ICMP type 3, code 9 or 10, TCP RST, or TCP ACK?

This answer says there are a few ways of dealing with a blocked packet at a firewall: At each of these levels a 1st IP packet (and any other protocol packet as an ESP or AH packet) might receive ...
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Promiscuous mode and packet sniffing

Is it must for a packet sniffer to enable promiscuous mode?Can packets be sniffed without the NIC being in promiscuous mode? Also when in promiscuous mode the NIC accepts all packets which are not ...
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Is there any reason that captive portal server can't block the ICMP echo request/reply packet

We can get connected to those public WiFi hotspot without the account but can access to no website but the login page. As I tested, all those login website would respond to my ping even I was an ...
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localhost to localhost ICMP traffic that is suspicious.. any idea of what is creating this?

I keep seen this on my tcpdump output.. is prob something very simple and logical but I can't see to see any process with lsof or netstat doing a ICMP request to it's own 127.0.0.1 every 2-3 secs... ...
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Security risk of allowing ICMP “destination unreachable” packets on AWS

If I configure an Amazon AWS VPC, should I explicitly allow ICMP "destination unreachable" packets inbound? I am wanting the VPC firewall to block everything by default, however does this mean this (...
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For what is an ICMP tunnel useful and how does ist work?

For what is it usefull? I (client) send an echo-request (with http data) to the proxy server. Then the proxy has to send me the echo-reply. But my question now is: 2.1 The proxy first needs to send ...
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Block Packets in snort

In rules configuration of snort I have: alert tcp any any -> any any (msg:"HTTP Connection"; react:block;) However when I add: alert icmp any any -> any any (msg:"HTTP Connection"; react:...
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Computer sending unstopped ICMP echo request to an IP

I noticed while hanging in Microsoft Network Monitor that my computer is sending ICMP echo request to an arbitrary IP address 202.39.253.11. I looked for the owner of this IP and I found it is owned ...
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Why is ICMP timestamping disabled on OS X?

It would seem like ICMP timestamping is quite a useful feature for troubleshooting networks with asymmetric paths. Replies to icmp(4) timestamp requests are generated by the kernel: On OpenBSD, the ...
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Disabling Ping/ICMP Requests [duplicate]

Are there any benefits from disabling Ping/ICMP requests on servers? I've read where people say to do it but I can't seem to find any real benefits with it. Only more likely to cause more problems. ...
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Wireshark Gratuitous ARP

I'm playing around with scapy and wireshark and I have sent a packet to a destination that does not exist (10.0.2.14). Wireshark shows an ARP attempt to resolve the address but as its not there the ...
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how to handle error reply messages?

For security reasons, many organizations do not allow error reply messages to leave their internal Internets. How, specifically, could hackers use information in echo reply messages to learn about the ...
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Is it a bad idea for a firewall to block ICMP?

This question was inspired by this answer which states in part: The generic firewall manifest file finishes off by dropping everything I didn't otherwise allow (besides ICMP. Don't turn off ICMP). ...
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IP attack by reading/writing data?

If I remember correctly there is an ICMP attack whereby you can embed malicious code and it gets read/executed, causing the problem (similar to SQL injection). Are there any further/more dangerous ...
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Is there any risk in allowing ping packets *out* through a firewall

The company I'm currently doing work for does not allow ping requests out through their firewall, for "security reasons" and I'm baffled as to why this is a concern. Before you point me to (e.g.) ...
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Differentiate normal flow and broadcast attacks

How do you identify whether a broadcast traffic is normal or is considered an attack such as a DoS attack?, There is some information that the plot or the source that allows me to differentiate ...
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ICMP redirects and source routing in the wild?

Theoretically, ICMP redirect messages (IPv4 and IPv6) and source routing (IPv4) / routing headers (IPv6) are very dangerous. However, I'm curious as to if attacks using these features really work in ...
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Security risk of PING?

I have been told that PING presents a security risk, and it's a good idea to disable/block it on production web servers. Some research tells me that there are indeed security risks. Is it common ...