1
vote
0answers
109 views

Only ICMP traffic allowed inbound on ISA Server 2006

I have recently set up a connection to a remote site. The connection between the sites is done at the ISP level (ie, this is not a B2B tunnel on ISA). I'm fairly lightweight in the networking realm, ...
0
votes
1answer
447 views

ICMP time exceeded in-transit

In the last few days my server suffers an attack of this kind: (bandwith > 60MBit/s, XXX.XXX.XXX.XXX are multiple IPs) tcpdump -n proto ICMP 17:15:19.267464 IP XXX.XXX.XXX.XXX > my_ip: ...
1
vote
1answer
99 views

Cisco ASA 5500 - Internet connection dies when adding ICMP exception to firewall

When I add ICMP to be allowed both on inside / outside interfaces the internet connection dies. Does anyone know why this happens? I kind of observed that this behavior takes place not just for ICMP. ...
0
votes
1answer
427 views

Pros vs Cons of Rate Limiting ICMP [duplicate]

I am configuring Config Server Firewall and here is the default config for ICMP. I have read on the internet that disabling or limiting ICMP can cause huge headaches on your server. However I have ...
4
votes
3answers
5k views

Denying ICMP type 3 code 4 traffic - good or bad?

Investigating a slow VPN connection (Cisco ASA IPSec) to a remote office, I noticed on our firewall a lot of access rule matches: Denied ICMP type=3, code=4 from *ip_address* on interface outside I ...
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 ...
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 ...
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 ...
5
votes
6answers
6k views

Why block outbound ICMP?

This question is slightly related to "Why Block Port 22 Outbound?". I don't see how this can be a notable security risk.