I will try explaining more my situation.

As I understand, a simple port scanning would first send a SYN probe packet, then if it receives a packet with SYN and ACK flags, the port should be open...

I am doing a pentest on a friend's server, and from my main OS (ubuntu), nmap shows a few open ports, but from a Backtrack 4 I have in a virtual machine (virtualbox), I get the same ports filtered.
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My problem was apparently the USB adapter, I replaced it with a new one and now it works perfectly.

Thanks everyone for the help.

I did read that link but I choose to ignore your comment (not trying to disrespect you) and read those that could lead me to solve my problem, beyond that my question cawas if bt4 includes the latest...

wlan0 is the onboard iwl3945
wlan1 is the usb adapter that uses rtl8187

These are the commands I tried

# airmon-ng stop wlan1
# airmon-ng start wlan1 X (X = channel)
# airodump-ng -c X...

I am using backtrack 4 (installed on hdd) on a hp530 laptop. I don't use the onboard wireless card iwl3945.

I have two USB adapters, one with rtl8187 and another with zd1211rw. I tested injection...

So it looks like i need to use a table of precomputed hashes or a wordlist.

Are the precomputed hashes used only for better speed when cracking the key or is there other benefit?

Because if...

AFAIK wep cracking is done by brute force and using statistical mathematics to get a better probability of guessing the key.

Anyway, I would like to know the basics of how WPA cracking works, I...

I think vmdk to vdi can also be done without qemu, using vditool from virtualbox, not sure but I think I read a tutorial somewhere that used only vditool

I haven't tried vm player on linux, I did used it on win and I was pretty happy with it. But I installed virtualbox on linux because I already had it downloaded, I guess I should try vm player on...

I notice that in the downloads area there's a vm image for vmware, what about virtualbox? Should I use the Final Release or convert the vmdk of the vmware image to vdi?

I was checking the metasploit tools and with ./module_ports.rb (which lists the exploits by the port they use) I get 156 exploits, and with ./module_targets.rb (which lists the target for each...

I downloaded the .run file from metasploit web apt-get will show me Couldn't find package.

Is there a way to uninstall Metasploit from linux? Should I just remove it folder?

I am using ubuntu where I installed metasploit but now I've downloaded bt4 so I wanted to uninstall metasploit...