-4
votes
2answers
46 views

How to manage PING replies? [closed]

How can I manage, for example, my Ubuntu mashine so it doesn't (or does) respond to PING(ICMP ECHO_REQUEST - type 8) requests? Normally almost all computers in a LAN network responds to ping with an ...
0
votes
1answer
32 views

Iptables REJECT doesn't let the ftp server list files

I had to comment these 2 lines in my iptables file, because for some reason it was denying ftp listing (it does connect to the ftp server, but it never lists the files and then it just times out): -A ...
0
votes
1answer
74 views

How can I proxy ICMP requests?

I have a ubuntu server that receives many ping requests from various other servers in the network. I would like to be able to proxy these requests. Using iptable rules I can see how to DROP or ACCEPT ...
0
votes
2answers
400 views

How to properly drop ICMP type 3 packets on possible DDoS attack?

Even after running iptables -A INPUT -p icmp -m icmp --icmp-type 3 -j DROP I keep getting ICMP type 3 code 13 packets on tcpdump. when I run tcpdump icmp, I get messages like: 19:41:31.923630 IP ...
0
votes
0answers
122 views

Multihoming, NAT and ICMP

My router is the default gateway of a LAN and is multihomed. ISP2 is used for HTTP, HTTPS and ISP1, the default gateway of the default routing table, for the rest of the traffic. Similar questions ...
0
votes
2answers
104 views

Restricting ICMP using iptables

I have the following rule,which i believe will restrict icmp packets to 1/s. :INPUT DROP [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [7:988] -A INPUT -i lo -j ACCEPT -A INPUT -p icmp -m icmp ...
1
vote
1answer
892 views

What exactly do --limit 1/s and --limit-burst mean in iptables rules?

centos 5.x I'm trying to wrap my mind around the following iptables rule on one of my servers: -A RH-Firewall-1-INPUT -p icmp --icmp-type echo-request -m limit --limit 1/s -j ACCEPT On another ...
5
votes
4answers
1k views

How to stop a ICMP attack?

We are under a heavy icmp flood attack. Tcpdump shows the result below. Altough we have blocked ICMP with iptables tcpdump still prints icmp packets. I've also attached iptables configuration and ...
1
vote
0answers
727 views

Why is my CentOS box rejecting some (but not all) ICMP ping requests from the same remote host?

CentOS 4.x I've got several old CentOS 4.x systems and have configured iptables to allow ICMP traffic. Originally, I had an iptables rule that looked like: -A RH-Firewall-1-INPUT -p icmp ...
7
votes
2answers
6k views

Why do ICMP Redirect Host happen?

I'm setting up a Debian box as a router for 4 subnets. For that I have defined 4 virtual interfaces on the NIC where the LAN is connected (eth1). eth1 Link encap:Ethernet HWaddr ...
11
votes
2answers
7k views

Does traceroute use UDP or ICMP or both?

When I do a trace on the www.google.com domain from my laptop, am I using icmp or udp ? I thought it was icmp type 11 but while searching for something else I came across rules where icmp type 30 was ...
5
votes
2answers
1k views

iptables | Types of ICMP: which ones are (potentially) harmful?

I read that certain types┬╣ of ICMP packets can be harmful. Questions: Which ones and why? How should I layout an iptables ruleset to handle each type of ICMP packet? Should I rate-limit any of these ...
0
votes
2answers
248 views

Linux not sending ICMP with iptables `--reject-with`

Using iptables I am trying to reject packets (I want to return an ICMP message). iptables -A FORWARD [...] -j REJECT --reject-with icmp-port-unreach The packets are dropped but using tcpdump I can ...
1
vote
3answers
1k views

Iptables not allowing ICMP requests from remote machines

I've configured my linux router with the following iptables rules iptables --list-rules -P INPUT ACCEPT -P FORWARD ACCEPT -P OUTPUT ACCEPT -A FORWARD -i vmbr0 -o eth2 -j ACCEPT -A FORWARD -i vmbr0 ...
1
vote
1answer
476 views

iptables owner match drops icmp for GIDs but not for UIDs

I have a strange behaviour of iptables that I cannot explain or understand. I have a user test which has its primary group test. I want to block any network access from this user. Now, if I say ...
1
vote
1answer
290 views

What do the extra parts of the iptables ping log entry mean?

I'm dropping all ICMP type 8 packets on the INPUT chain and so now I'm seeing log entries as a Fabric script tries to contact another server, like this: kernel: INPUT DROP IN=eth0 OUT= ...
0
votes
1answer
675 views

iptables can't block timestamp request with CentOS

I am setting up firewall with iptables on my host. I want to disable timestamp ICMP request, but it's wired, I only allows type 8 (echo-request) comes into host, but event still, I can get timestamp ...
0
votes
1answer
79 views

What firewall changes could cause a drastic increase in spam?

I created some iptables rules, basically allowing incoming traffic from TCP/UDP Ports 80,53(for the bind server), 22, and blocking everything else incoming however I forgot to allow the ICMP protocol ...
2
votes
1answer
1k views

Why isn't ICMP routing with iptables nat routing

I'm using iptables on Ubuntu server to route a public IP to a private IP. I want to nat all traffic, including 80, 443 and ICMP. However, it appears that ICMP isn't routing. I have a steady ping ...
29
votes
8answers
12k views

Why not block ICMP?

I think I almost have my iptables setup complete on my CentOS 5.3 system. Here is my script... # Establish a clean slate iptables -P INPUT ACCEPT iptables -P FORWARD ACCEPT iptables -P OUTPUT ACCEPT ...