Re: last log related question
sorry, forgot to sent it to the list... - Forwarded message from Volker Dormeyer - Date: Tue, 1 Jan 2002 19:46:40 +0100 Subject: Re: last log related question To: eim [EMAIL PROTECTED] Hello, On Tue, Jan 01, 2002 at 06:30:56PM +0100, eim [EMAIL PROTECTED] wrote: First of all Happy new Year to everyone on this list ! thanks, same to you. Last time I logged in as root and ran the command 'last' I saw that there where no logs, the output was just: ~# last root wtmp begins Tue Jan 1 18:29:15 2002 That's all, anyone has hacked my box and deleted my last logs ? Or just some 'crontab-joke' ? The last command looks at /var/log/wtmp. The wtmp log on debian rotates monthly via logrotate. Take a look at /etc/logrotate.conf for logrotate configuration. It's started by cron - look at etc/cron.daily/logrotate. regards, Volker -- Volker Dormeyer # [EMAIL PROTECTED] - End forwarded message - -- Volker Dormeyer # [EMAIL PROTECTED]
Re: Port Scan for UDP
Hi, On Sun, Oct 21, 2001 at 05:47:11PM +0200, Petre Daniel [EMAIL PROTECTED] wrote: also netstat -n -p -t --listening | grep :PORT sure, but it shows you only tcp connections. regards, Volker VD You can also use netstat -pan to find out which process is listening on VD which port. -- Volker Dormeyer * [EMAIL PROTECTED] PGP signature
Re: Port Scan for UDP
thanks for your explanation. regards, Volker On Sun, Oct 21, 2001 at 10:45:28AM -0500, Craig McPherson [EMAIL PROTECTED] wrote: I can't believe nobody has answered this correctly yet. UDP is different than TCP in that it is a stateless protocol, and that means you have to understand a few things to interpret UDP port scan results correctly. With TCP scans, you get one of three results: OPEN (meaning that the TCP handshake sequence to open a connection completed), CLOSED (meaning that the target sent a port closed ICMP message), or FILTERED (meaning that no response was received at all: this is also called stealthed by so-called security experts like Steve Gibson but it's a good idea to ignore him just on general principles). UDP is a completely stateless protocol, though. Even if you send a UDP packet to a port that a valid daemon is listening on, the system isn't obligated to send anything back to you at all: there is no handshake sequence to establish a connection. So making a determination is harder than with TCP. If you receive a port closed ICMP message, the port can be safely listed as CLOSED, but if you receive nothing at all, that could mean that the port is either OPEN or FILTERED -- it's pretty much impossible to tell the difference. NMAP assumes that every UDP port that it doesn't receive a responsee from is OPEN, which means that if you have your firewall DROP all UDP connections, every UDP port will appear as open. If you want to fix this, have your firewall REJECT instead of DROP, and the ports will appear correctly as CLOSED to a port scan. DROPing connections without a response is in violation of the RFCs, too, if you care about that sort of thing. Having the local machine portscan itself will also tell you which UDP ports are *actually* open, because I assume you don't have your firewall set to DROP packets from itself. Also, did you know that by default, nmap only scans ports listed in its services file? So although it scans commonly-used ports, it's not scanning the entire system. If you have enough time (this will make the scan very slow, especially over a slow network link), use the -p 1- argument to every scan to force nmap to scan every port from 1 to 65535 instead of just the maybe 400 or 500 ports that it has listed in its services file. That's the only way you can get a complete picture of what your box looks like from the outside. I'm doing portscans on a system I'm working to learn more about securing hosts and setting up iptables. My tcp portscan reported what I expected, only www, ssh and smtp listening. The udp portscan reported a huge list of 'open' ports. I really didn't know what to expect for this scan, so I want to know if this is normal. Just for grins, I removed every udp listing in /etc/services and restarted inetd and the scan came back the same. I figure this is normal, but if someone can confirm this behaviour, I'd really appreciate it. If this isn't secure behaviour, perhaps I can add an iptables entry like: iptables -A INPUT -p udp -j drop However, I don't have any applications running using udp, so the 'open' port doesn't have anywhere to go, as far as I know. Again, if someone can confirm this, I'd really appreciate it. thanks, jc -- Craig McPherson Information Technology Coordinator Baptist Collegiate Ministry -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED] -- Volker Dormeyer * [EMAIL PROTECTED] -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: Port Scan for UDP
Hi, On Sat, Oct 20, 2001 at 09:22:57PM -0700, tony mancill [EMAIL PROTECTED] wrote: On Sat, 20 Oct 2001, Marc Wilson wrote: Adding or removing lines in /etc/services doesn't open or close ports... this is a common misconception. Removing what's listening on a particular port is what closes that port. A good way to find out what process is listening on a port is to load the lsof package and use lsof -i (as root so that you'll see everything). You can also use netstat -pan to find out which process is listening on which port. regards, Volker -- Volker Dormeyer * [EMAIL PROTECTED] pgpGr1EqzpSUn.pgp Description: PGP signature
Re: Port Scan for UDP
Hi, On Sun, Oct 21, 2001 at 05:47:11PM +0200, Petre Daniel [EMAIL PROTECTED] wrote: also netstat -n -p -t --listening | grep :PORT sure, but it shows you only tcp connections. regards, Volker VD You can also use netstat -pan to find out which process is listening on VD which port. -- Volker Dormeyer * [EMAIL PROTECTED] pgpUzJJBXRgKZ.pgp Description: PGP signature
Re: Port Scan for UDP
thanks for your explanation. regards, Volker On Sun, Oct 21, 2001 at 10:45:28AM -0500, Craig McPherson [EMAIL PROTECTED] wrote: I can't believe nobody has answered this correctly yet. UDP is different than TCP in that it is a stateless protocol, and that means you have to understand a few things to interpret UDP port scan results correctly. With TCP scans, you get one of three results: OPEN (meaning that the TCP handshake sequence to open a connection completed), CLOSED (meaning that the target sent a port closed ICMP message), or FILTERED (meaning that no response was received at all: this is also called stealthed by so-called security experts like Steve Gibson but it's a good idea to ignore him just on general principles). UDP is a completely stateless protocol, though. Even if you send a UDP packet to a port that a valid daemon is listening on, the system isn't obligated to send anything back to you at all: there is no handshake sequence to establish a connection. So making a determination is harder than with TCP. If you receive a port closed ICMP message, the port can be safely listed as CLOSED, but if you receive nothing at all, that could mean that the port is either OPEN or FILTERED -- it's pretty much impossible to tell the difference. NMAP assumes that every UDP port that it doesn't receive a responsee from is OPEN, which means that if you have your firewall DROP all UDP connections, every UDP port will appear as open. If you want to fix this, have your firewall REJECT instead of DROP, and the ports will appear correctly as CLOSED to a port scan. DROPing connections without a response is in violation of the RFCs, too, if you care about that sort of thing. Having the local machine portscan itself will also tell you which UDP ports are *actually* open, because I assume you don't have your firewall set to DROP packets from itself. Also, did you know that by default, nmap only scans ports listed in its services file? So although it scans commonly-used ports, it's not scanning the entire system. If you have enough time (this will make the scan very slow, especially over a slow network link), use the -p 1- argument to every scan to force nmap to scan every port from 1 to 65535 instead of just the maybe 400 or 500 ports that it has listed in its services file. That's the only way you can get a complete picture of what your box looks like from the outside. I'm doing portscans on a system I'm working to learn more about securing hosts and setting up iptables. My tcp portscan reported what I expected, only www, ssh and smtp listening. The udp portscan reported a huge list of 'open' ports. I really didn't know what to expect for this scan, so I want to know if this is normal. Just for grins, I removed every udp listing in /etc/services and restarted inetd and the scan came back the same. I figure this is normal, but if someone can confirm this behaviour, I'd really appreciate it. If this isn't secure behaviour, perhaps I can add an iptables entry like: iptables -A INPUT -p udp -j drop However, I don't have any applications running using udp, so the 'open' port doesn't have anywhere to go, as far as I know. Again, if someone can confirm this, I'd really appreciate it. thanks, jc -- Craig McPherson Information Technology Coordinator Baptist Collegiate Ministry -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED] -- Volker Dormeyer * [EMAIL PROTECTED]
Re: Port Scan for UDP
Hi, On Sat, Oct 20, 2001 at 09:22:57PM -0700, tony mancill [EMAIL PROTECTED] wrote: On Sat, 20 Oct 2001, Marc Wilson wrote: Adding or removing lines in /etc/services doesn't open or close ports... this is a common misconception. Removing what's listening on a particular port is what closes that port. A good way to find out what process is listening on a port is to load the lsof package and use lsof -i (as root so that you'll see everything). You can also use netstat -pan to find out which process is listening on which port. regards, Volker -- Volker Dormeyer * [EMAIL PROTECTED] PGP signature
