Shields up - Whats up

information

If you understand what shields up does, what its limitations are, what it can tell you, what it can't tell you, what is between you and shields up, etc, then it isn't necessarily worthless. I just ran it against my present location and failed miserably, but I know why so I don't care.

There are many other similar online tools. Most of them will turn up here

Jason

Such tools all suffer from the problem, that maybe on the route in between things are filtered, which are not from another route.

So it's much better to scan your host locally. Just use a second host on the same network, and nmap -sS -P0

Yours, VB.

Right. It's ridiculous, and makes life somewhat happier ;-)

Yours, VB.

but what if you want to test the router/firewall/nat device that the comps are connected to?

well. if a local scan really can't do it, then it's not an alternative to the web scan interfaces.

so, i'm wondering 'what would VB do?'

off topic slightly, Regarding alternatives - what i would do until I see a better idea

and I can think of alternatives to a web interface too, without asking friends or neighbours!!!

An alternative to online scan would be to have a comp outside the network. plug the comp into the phone socket and dial up to an ISP. So you have an IP outside that network sending packets to your network going throguh that router/firewall/NAT device. In the UK dial up isn't free though. And you need to have a comp to take off your network to do the test. You get a good test though, you can use nmap. But web scan wins hands down for convenience.

I've only read book about real routers, but maybe if you have a proper router, then you can connect a 2 port switch to one port. Connect one port to the internet. On the other port put a computer. So now you can test your comp as if from the internet, using nmap. perhaps.

It appears to me that there is no convenient way to avoid web interfaces. A local scan doesn't seem like an an alternative . I'm sure i'm wrong though. I'm hoping i'm wrong. i'm wondering 'what would VB do ;) ' since he seems by to think that online web scans are not necessary.

Maybe some other comp somewhere on the internet, always on, that he can telnet to and run nmap from. But if it's accessible from anywhere, that's hard to secure. Academic institutions tend to offer this sort of thing and let any IP through.

Or if it is a stand alone?

I don't know what you mean "second box at the same provider"

second computer? second router? I don't understand either way.

At the moment I have My Computers to my NAT device to the wall to my ISP's Router.

There are no options for a second anything between the wall and my ISP's router. I can't even see behind there!! ;)

Between my NAT device and the wall, there can only be a telephone cable.

The only place on the NAT device where I can put anything other than the telephone cable is in the switch built into the NAT device. So I woudln't be testing my NAT device from the outside. Unless I used an online scanner. My NAT device has a built in firewall too, and of course port forwarding facility, so it's important to check it from the outside.

So, when you say "second box at the same provider" I suppose you're assuming I have a better set up!!!

I am thinking of a real router. Use 2 interfaces. Putt a switch on one interface, hooking that up to the itnernet and to a computerA. Then on the other interface I have the comps on my LAN. Then, compuoter A can access my LAN from the outside.

I don't know what you mean by "second box at the same provider". What setup should I have?

The idea is to port scan from the internet, or from outside my LAN, outside my router or nat device. I googled "second box at the same provider" but no luck!

Either scan yourself from another computer with another IP address (Such as a friend or neighbor's computer) or use the online tools.

Jason

What would he be looking out for?

Then a test in the same network is useful also. Perhaps with a second box at the same provider, if you want to test what's behind DSL, for example.

Yours, VB.

VB would do a netstat -ano or a lsof -i and check, what's offered. This is best anyway. ;-)

Yours, VB.

It is certainly best to know what is offered. In other words it is best to know what the results of a scan will be before you do it. I frequently use online tools to run scans, even shields up sometimes, but I nearly always get the result I knew I'd get and if I get an unexpected result then I'll compare it with the result from a different online tool or do other tests to find out why there's a discrepancy. Using shields up for a quick test doesn't mean I have to read or believe anything on the shields up site.

Jason

And then?

He'd looking out for processes listen()ing, and not listen()ing on localhost 127.0.0.1.

Yours, VB.

If there is noting which listen()s, then there is nothing I need to filter.

And if a test from outside is showing something, then this is an error in this test.

Yours, VB.

With a second computer, which uses the same infrastructure to connect, you'll have a very short route and usually nothing filtering in between.

What I mean is, that with a second account at the same provider, a second connection is used.

Just use a second "telephone cable" and a second connection. Perhaps you are having a friend, who uses the same connection type in your neighborhood?

In this case you're right. Aren't you able to have a second way to reach the Internet? Then a simple nmap -sS -P0 $actual_ip_address will do.

A friend with the same connection type, or just another computer with Internet connection, if that isn't possible.

To make that clear: I have nothing against online scans, if they're not from Gibson or some other guys I don't trust at all. If you have a Webpage, who documents exactly _how_ the scan is done, and you trust in that, then you can use this way either, if no other way is suitable for you.

Usually you're seeing immediately, if you cannot trust such a Webpage: if they're babbling about "stealth ports" ;-)

This is important for security purposes anyway: think yourself. Don't believe too much. Test it yourself. Try it out, and try to understand.

Yours, VB.

On 13 Sep 2005 22:34:59 +0200, Volker Birk spoketh

Actually, anything listening on 127.0.0.1 would be harmless anyways, as it would only accept local (host) connections.

The things to look out for are anything listening on 0.0.0.0 or the actual IP address of the machine.

Lars M. Hansen

Netstat "listening" isn't always accurate. Below is a paste from a article by Marchand:

The second line shows the established connection, from local port 1367 to remote port 22. However, the first line is incorrect because it reports local port 1367 in the LISTENING state, whereas no TCP server is available on this port.

Thus, for each outgoing TCP connection, an additional line will appear in netstat output, showing a TCP port in LISTENING state. It is important to make the difference between an opened TCP port and one incorrectly reported by netstat in the LISTENING state.

Note: this bug has been fixed in Windows Server 2003.

Art

Yes.

Yes. As I stated, _not_ listening on 127.0.0.1.

Yours, VB.