Ping against server will work if firewall allows ICMP probes.
If a server service is listening on port N, a simple telnet IP port will tell you that.
Something like :
This tells me that 4.59.125.171 has a port 80 open are receiving requests.
For further (security ) analysis nmap is the best tool.
Port Scanning is Not a Crime but acting on its results can be, especially on government and financial sites.
I can ping other computers in my office. I can telnet other users in my office but i cannot get out of the office network. If i try to go out side of my network it cannot find host.
Any ideas? (5 Replies)
Hi,
Can anybody help me out why l can't not ping my server with Openserver 5.0.4 with my windows machine from a remote site.
The machine could see the local LAN with the Router however, i can't ping or telnet unto the server from another site on the WAN. The default gateway was configure on the... (0 Replies)
Hi All,
We are not able to ping to a AIX box...Network is ok..when we give ping from that AIX box..it is giving 0821-067 ping: The socket creation call failed.there is no enough buffer space for the requested socket operation.
refresh -s inetd is also giving socket error.
Please help to... (1 Reply)
I have one problem and it is giving me hard time
I can ping my windows machine
root@x1ChXpress:/sbin
>ping 192.168.129.66
192.168.129.66 is alive
root@x1ChXpress:/sbin
>netstat -rn
Routing Table:
Destination Gateway Flags Ref Use Interface... (3 Replies)
I have two redhat linux server. i have created one script which contain some command that run on Local server as well as remote server.I am using this command to connect to remote server
ssh user1@192.x.x.x 'command'
but when i am running the script in local server it connecting to the server... (1 Reply)
We have a Sun Solaris Netra 20 server. Our O&M Server gets Alarm Processor
not responding. When Alarm occurs, you can ping the sun server but cannot telnet it. We keep getting Interrupt level not serviced. var/adm/message log is
> tail -f messages
Apr 12 20:09:56 cama pcisch: PCI-device:... (9 Replies)
Hi all,
I am not sure if my problem is specific to HP-UX or not. Hopefully someone can tell me what's wrong.
I have a server name server1 10.100.50.10 in the /etc/hosts file and if I do a ping server1, it shows the right IP address.
However, if I run telnet server1, it is not using... (4 Replies)
Hi,
After a crash of our older AIX server it happend as it is in the title:
ping is ok, but telnet:
What it can be this strange thing?
Franci (2 Replies)
Hello,
I need help, I have the following which save in the result file ping and telnet:port test.
Basically the script works but I should implement a check on ping and telnet command so that ping has 5 seconds threshold and telnet (more important) 10 seconds. Over that threshold ping and... (0 Replies)
Discussion started by: marmellata
0 Replies
LEARN ABOUT DEBIAN
blackhole
BLACKHOLE(4) BSD Kernel Interfaces Manual BLACKHOLE(4)NAME
blackhole -- a sysctl(8) MIB for manipulating behaviour in respect of refused TCP or UDP connection attempts
SYNOPSIS
sysctl net.inet.tcp.blackhole[=[0 | 1 | 2]]
sysctl net.inet.udp.blackhole[=[0 | 1]]
DESCRIPTION
The blackhole sysctl(8) MIB is used to control system behaviour when connection requests are received on TCP or UDP ports where there is no
socket listening.
Normal behaviour, when a TCP SYN segment is received on a port where there is no socket accepting connections, is for the system to return a
RST segment, and drop the connection. The connecting system will see this as a ``Connection refused''. By setting the TCP blackhole MIB to
a numeric value of one, the incoming SYN segment is merely dropped, and no RST is sent, making the system appear as a blackhole. By setting
the MIB value to two, any segment arriving on a closed port is dropped without returning a RST. This provides some degree of protection
against stealth port scans.
In the UDP instance, enabling blackhole behaviour turns off the sending of an ICMP port unreachable message in response to a UDP datagram
which arrives on a port where there is no socket listening. It must be noted that this behaviour will prevent remote systems from running
traceroute(8) to a system.
The blackhole behaviour is useful to slow down anyone who is port scanning a system, attempting to detect vulnerable services on a system.
It could potentially also slow down someone who is attempting a denial of service attack.
WARNING
The TCP and UDP blackhole features should not be regarded as a replacement for firewall solutions. Better security would consist of the
blackhole sysctl(8) MIB used in conjuction with one of the available firewall packages.
This mechanism is not a substitute for securing a system. It should be used together with other security mechanisms.
SEE ALSO ip(4), tcp(4), udp(4), ipf(8), ipfw(8), pfctl(8), sysctl(8)HISTORY
The TCP and UDP blackhole MIBs first appeared in FreeBSD 4.0.
AUTHORS
Geoffrey M. Rehmet
BSD January 1, 2007 BSD