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Wednesday, August 27, 2008
In Fyodor’s talk at Blackhat he talked about the research he’s been doing, and the ways that research has helped him to improve Nmap with lot many enhancements. Let's have a look at the most interesting one.
Abstract:
One of Fyodor’s main focuses was improving Nmap’s speed through improved
efficiency. One of the best ways to do this is to allow for scans of fewer
ports, but this requires that you choose those ports carefully so as to miss as
little as possible. So what he did, through trial and error and tons of scans,
was figure out the most frequently open ports on the Internet.Here they are for each protocol:
TCP
- 80
- 23
- 22
- 443
- 3389
- 445
- 139
- 21
- 135
- 25
UDP
- 137
- 161
- 1434
- 123
- 138
- 445
- 135
- 67
- 139
- 53
Ok, so now that we know what the top 10 ports are, wouldn’t it be cool to be
able to scan based on them? And what if we wanted to scan the top 50? Or the top
100?Fyodor has built this in with the
--top-portsoption. It’s
wicked nice, and you invoke it like this:nmap –top-ports 100 $target
And of course, 100 is just an arbitrary number, so you could just as easily
do this:nmap –top-ports 3000 $target
As you increase this number you obviously gain more and more accuracy, but
because the ports are organized according to the most commonly found on the
Internet, you can scan relatively few and still have good chances of finding
everything open.Stats from his presentation on TCP port efficiency using
--top-ports:–top-ports 10: 48%
–top-ports 50: 65%
–top-ports 100: 73%
–top-ports 250: 83%
–top-ports 500: 89%
–top-ports 1000: 93%
–top-ports 2000: 96%
–top-ports 3764: 100%This means for just curiosity scans I can go with
--top-portsand get roughly 93% accuracy in a fraction of the time.
1000
read about more options here.
Here is a view from my window the flight standing next is a similar one (ATR-42-320)
And this is the strappy net thing which made me feel like skydiving. And yes thats the elder aunt standing outside the cockpit.
I saw this girl standing outside when we were boarding but later on she turned out to be some instructor or ground crew member without a uniform or proper props. She was signaling the pilot to start and take a turn as if she was signaling a truck and guiding the parking of it.
Then came the time on serving breakfast, the elderly aunt brought a basket of muffin and puffs. It was served in just a tissue paper, no plates, and no condiments nothing. And then water was served. The first thing I did in this case was checking the seal of bottle and packing date. Atleast that was all ok.
Day before of my flight, one of my friend suggested me not to take a flight to Jaipur as the driving time is only 3 hours with wonderful roads, but I had already booked so ignored her suggestion. In the flight I was thinking, why I ignored her. I should have taken the road route, in any case it took me same time in the flight too.
This was at the moment when Li Ning was rounding the lip of the Bird's Nest during the amazing torch-lighting climax.
