You didn't say how slow your scans get, but I think you would benefit from playing with the --min-parallelism
option, which adjusts the minimum number of outstanding probes.
I'm seeing 70% reductions in scan time (compared with bare -sT
-sU
scans) like this. Note that it is possible to set --min-parallelism
too high, such that the host (or network) cannot buffer this many queries simultaneously.
[mpenning@Hotcoffee]$ sudo nmap --min-parallelism 100 -sT -sU localhost
Starting Nmap 5.00 ( http://nmap.org ) at 2012-05-10 01:07 CDT
Interesting ports on localhost (127.0.0.1):
Not shown: 1978 closed ports
PORT STATE SERVICE
22/tcp open ssh
25/tcp open smtp
49/tcp open tacacs
53/tcp open domain
80/tcp open http
111/tcp open rpcbind
631/tcp open ipp
2003/tcp open finger
2004/tcp open mailbox
3389/tcp open ms-term-serv
5901/tcp open vnc-1
5910/tcp open unknown
6001/tcp open X11:1
7002/tcp open afs3-prserver
53/udp open|filtered domain
69/udp open|filtered tftp
111/udp open|filtered rpcbind
123/udp open|filtered ntp
161/udp open|filtered snmp
631/udp open|filtered ipp
1812/udp open|filtered radius
1813/udp open|filtered radacct
Nmap done: 1 IP address (1 host up) scanned in 1.54 seconds
[mpenning@Hotcoffee]$