Tuesday, June 30, 2015
Thursday, June 25, 2015
nmap: scanning for conficker
nmap -p139,445 --script p2p-conficker,smb-os-discovery,smb-check-vulns --script-args=smbuser=*****,smbpass=*****,checkconficker=1,safe=1 -T4 192.168.1.100-254
Bad results look like this
Nmap scan report for 192.168.1.253 Host is up (0.00018s latency). PORT STATE SERVICE 139/tcp open netbios-ssn 445/tcp open microsoft-ds MAC Address: 70:71:BC:0E:00:92 (Pegatron) Host script results: | smb-check-vulns: | MS08-067: CHECK DISABLED (add '--script-args=unsafe=1' to run) | Conficker: Likely INFECTED (by Conficker.C or lower) | regsvc DoS: CHECK DISABLED (add '--script-args=unsafe=1' to run) | SMBv2 DoS (CVE-2009-3103): CHECK DISABLED (add '--script-args=unsafe=1' to run) | MS06-025: CHECK DISABLED (add '--script-args=unsafe=1' to run) |_ MS07-029: CHECK DISABLED (add '--script-args=unsafe=1' to run) | smb-os-discovery: | OS: Windows XP (Windows 2000 LAN Manager) | OS CPE: cpe:/o:microsoft:windows_xp::- | Computer name: E10 | NetBIOS computer name: E10 | Workgroup: ********* |_ System time: 2015-06-26T02:06:02-07:00
Wednesday, June 3, 2015
How to match newlines in sed
Original: http://backreference.org/2009/12/23/how-to-match-newlines-in-sed/
Lots of sed newcomers ask why the following snippets of code, or some variation thereof, don't work (they actually work as expected; it's just that the results are not what they think should be):
# All these do NOT produce the expected result! sed 's/\n//g' # remove all newline characters sed 's/PATTERN\n// # if the line ends in PATTERN, join it with the next line sed 's/FOO\nBAR/FOOBAR/' # if a line ends in FOO and the next starts with BAR, join them
To understand why those "don't work", it's necessary to look at how sed reads its input.
Basically, sed reads only one line at a time and, unless you perform special actions, there is always a single input line in the pattern space at any time. That line does NOT have a trailing newline characters, because sed removes it. When the line is printed at the end of the cycle, sed adds back a newline character, but while the line is in the pattern buffer, there's simply no \n in it. Now it's easy to see why none of the above programs will do what you think: the lhs (left hand side) will never match what's in the pattern space, so no replacement will be performed. However, sed does add a newline when you ask it to perform certain commands.
Basically, sed reads only one line at a time and, unless you perform special actions, there is always a single input line in the pattern space at any time. That line does NOT have a trailing newline characters, because sed removes it. When the line is printed at the end of the cycle, sed adds back a newline character, but while the line is in the pattern buffer, there's simply no \n in it. Now it's easy to see why none of the above programs will do what you think: the lhs (left hand side) will never match what's in the pattern space, so no replacement will be performed. However, sed does add a newline when you ask it to perform certain commands.
So the next question is: how to do the things that the above programs wrongly attempted to do?
Three not-so well-known commands that are useful for these applications are N, P and D.
- N reads in another line of input and appends it to the current pattern space, separated by a newline;
- P prints the contents of the pattern space, up to the first newline (or to the end if there is no newline);
- D deletes the contents of the patterns space, up to the first newline (or to the end if there is no newline), and starts a new cycle. The latter means that any commands that come after the D in the sed program will not be executed if D itself is executed.
So let's put these commands to good use:
sed ':begin;$!N;s/\n//;tbegin' # deletes all newlines except the last; see also tr -d '\n' sed ':begin;$!N;s/\n/ /;tbegin' # same as before, but replaces newlines with spaces; see also tr '\n' ' ' sed ':begin;$!N;s/\(PATTERN\)\n/\1/;tbegin;P;D' # if the line ends in PATTERN, join it with the next line sed ':begin;$!N;/PATTERN\n/s/\n//;tbegin;P;D' # same as above sed ':begin;$!N;s/FOO\nBAR/FOOBAR/;tbegin;P;D' # if a line ends in FOO and the next starts with BAR, join them
The programs that join lines, above, keep joining lines as long as the conditions for joining with the next line are true. Note that the mentioned solutions based on trare not exactly equivalent, in that they will remove or replace the very last newline of the input too, meaning that the output won't be terminated by \n.
tcpdump tutorial from danielmiessler.com
tcpdump is the premier network analysis tool for information security professionals. Having a solid grasp of this über-powerful application is mandatory for anyone desiring a thorough understanding of TCP/IP. Many prefer to use higher level analysis tools such as
In a discipline so dependent on a true understanding of concepts vs.rote learning, it's important to stay fluent in the underlying mechanics of the TCP/IP suite. A thorough grasp of these protocols allows one to troubleshoot at a level far beyond the average analyst, but mastery of the protocols is only possible through continued exposure to them.
When using a tool that displays network traffic a more natural (raw) way the burden of analysis is placed directly on the human rather than the application. This approach cultivates continued and elevated understanding of the TCP/IP suite, and for this reason I stronglyadvocate using
tcpdump instead of other tools whenever possible.15:31:34.079416 IP (tos 0x0, ttl 64, id 20244, offset 0, flags [DF], proto: TCP (6), length: 60) source.35970 > dest.80: S, cksum 0x0ac1 (correct), 2647022145:2647022145(0) win 5840 0x0000: 4500 003c 4f14 4000 4006 7417 0afb 0257 E.. 0x0010: 4815 222a 8c82 0050 9dc6 5a41 0000 0000 H."*...P..ZA.... 0x0020: a002 16d0 0ac1 0000 0204 05b4 0402 080a ................ 0x0030: 14b4 1555 0000 0000 0103 0302
Options
Below are a few options (with examples) that will help you greatly when working with the tool. They're easy to forget and/or confuse with other types of filters, i.e. ethereal, so hopefully this page can serve as a reference for you, as it does me.
First off, I like to add a few options to the
tcpdump command itself, depending on what I'm looking at. The first of these is -n, which requests that names are not resolved, resulting in the IPs themselves always being displayed. The second is -X, which displays both hex and ascii content within the packet. The final one is -S, which changes the display of sequence numbers to absolute rather than relative. The idea there is that you can't see weirdness in the sequence numbers if they're being hidden from you. Remember, the advantage of usingtcpdump vs. another tool is getting manual interaction with the packets.
It's also important to note that 68 96 bytes of data from a packet by default. If you would like to look at more, add the -s number option to the mix, where number is the number of bytes you want to capture. I recommend using 0 (zero) for a snaplength, which gets everything. Here's a short list of the options I use most:
tcpdump only takes the first -i any: Listen on all interfaces just to see if you're seeing any traffic.-n: Don't resolve hostnames.-nn: Don't resolve hostnames or port names.-X: Show the packet's contents in both hex and ASCII.-XX: Same as-X, but also shows the ethernet header.-v, -vv, -vvv: Increase the amount of packet information you get back.-c: Only get x number of packets and then stop.-s: Define the snaplength (size) of the capture in bytes. Use-s0to get everything, unless you are intentionally capturing less.-S: Print absolute sequence numbers.-e: Get the ethernet header as well.-q: Show less protocol information.-E: Decrypt IPSEC traffic by providing an encryption key.
[ The default snaplength as of
tcpdump 4.0 has changed from 68 bytes to 96 bytes. While this will give you more of a packet to see, it still won't get everything. Use-s 1514 to get full coverage ]Basic Usage
So, based on the kind of traffic I'm looking for, I use a different combination of options to
tcpdump, as can be seen below:- Basic communication // see the basics without many options# tcpdump -nS
- Basic communication (very verbose) // see a good amount of traffic, with verbosity and no name help# tcpdump -nnvvS
- A deeper look at the traffic // adds -X for payload but doesn't grab any more of the packet# tcpdump -nnvvXS
- Heavy packet viewing // the final "s" increases the snaplength, grabbing the whole packet# tcpdump -nnvvXSs 1514
Here's a capture of exactly two (
-c2) ICMP packets (a ping and pong) using some of the options described above. Notice how much we see about each packet.hermes root # tcpdump -nnvXSs 0 -c2 icmp tcpdump: listening on eth0, link-type EN10MB (Ethernet), 23:11:10.370321 IP (tos 0x20, ttl 48, id 34859, offset 0, flags [none], length: 84) 69.254.213.43 > 72.21.34.42: icmp 64: echo request seq 0 0x0000: 4520 0054 882b 0000 3001 7cf5 45fe d52b E..T.+..0.|.E..+ 0x0010: 4815 222a 0800 3530 272a 0000 25ff d744 H."*..50'*..%..D 0x0020: ae5e 0500 0809 0a0b 0c0d 0e0f 1011 1213 .^.............. 0x0030: 1415 1617 1819 1a1b 1c1d 1e1f 2021 2223 .............!"# 0x0040: 2425 2627 2829 2a2b 2c2d 2e2f 3031 3233 $%&'()*+,-./0123 0x0050: 3435 3637 4567 23:11:10.370344 IP (tos 0x20, ttl 64, id 35612, offset 0, flags [none], length: 84) 72.21.34.42 > 69.254.213.43: icmp 64: echo reply seq 0 0x0000: 4520 0054 8b1c 0000 4001 6a04 4815 222a E..T....@.j.H."* 0x0010: 45fe d52b 0000 3d30 272a 0000 25ff d744 E..+..=0'*..%..D 0x0020: ae5e 0500 0809 0a0b 0c0d 0e0f 1011 1213 .^.............. 0x0030: 1415 1617 1819 1a1b 1c1d 1e1f 2021 2223 .............!"# 0x0040: 2425 2627 2829 2a2b 2c2d 2e2f 3031 3233 $%&'()*+,-./0123 0x0050: 3435 3637 4567 2 packets captured 2 packets received by filter 0 packets dropped by kernel hermes root #
Common Syntax
Expressions allow you to trim out various types of traffic and find exactly what you're looking for. Mastering the expressions and learning to combine them creatively is what makes one truly powerful with
tcpdump. There are three main types of expression: type, dir, andproto.
Type options are
host, net, and port. Direction is indicated by dir, and there you can have src, dst, src or dst, and src and dst. Here are a few that you should definitely be comfortable with:host// look for traffic based on IP address (also works with hostname if you're not using -n)# tcpdump host 1.2.3.4src,dst// find traffic from only a source or destination (eliminates one side of a host conversation)# tcpdump src 2.3.4.5
# tcpdump dst 3.4.5.6net// capture an entire network using CIDR notation# tcpdump net 1.2.3.0/24proto// works for tcp, udp, and icmp. Note that you don't have to typeproto# tcpdump icmpport// see only traffic to or from a certain port# tcpdump port 3389src, dst port// filter based on the source or destination port# tcpdump src port 1025
# tcpdump dst port 389src/dst, port, protocol// combine all three# tcpdump src port 1025 and tcp
# tcpdump udp and src port 53
You also have the option to filter by a range of ports instead of declaring them individually, and to only see packets that are above or below a certain size.
- Port Ranges // see traffic to any port in a range
tcpdump portrange 21-23 - Packet Size Filter // only see packets below or above a certain size (in bytes)
tcpdump less 32tcpdump greater 128
[ You can use the symbols for less than, greater than, and less than or equal/ greater than or equal signs as well. ]
// filtering for size using symbolstcpdump > 32tcpdump <= 128Writing to a File
tcpdump allows you to send what you're capturing to a file for later use using the -w option, and then to read it back using the -r option. This is an excellent way to capture raw traffic and then run it through various tools later.
The traffic captured in this way is stored in
tcpdump format, which is pretty much universal in the network analysis space. This means it can be read in by all sorts of tools, including Wireshark, Snort, etc.Capture all Port 80 Traffic to a File
# tcpdump -s 1514 port 80 -w capture_file
Then, at some point in the future, you can then read the traffic back in like so:
Read Captured Traffic back into tcpdump
# tcpdump -r capture_file
Getting Creative
Expressions are nice, but the real magic of
tcpdump comes from the ability to combine them in creative ways in order to isolate exactly what you're looking for. There are three ways to do combinations, and if you've studied computers at all they'll be pretty familar to you:- AND
andor&& - OR
oror|| - EXCEPT
notor!
More Examples
# TCP traffic from 10.5.2.3 destined for port 3389
tcpdump -nnvvS and src 10.5.2.3 and dst port 3389
# Traffic originating from the 192.168 network headed for the 10 or 172.16 networks
tcpdump -nvX src net 192.168.0.0/16 and dst net 10.0.0.0/8 or172.16.0.0/16
# Non-ICMP traffic destined for 192.168.0.2 from the 172.16 network
tcpdump -nvvXSs 1514 dst 192.168.0.2 and src net and not icmp
# Traffic originating from Mars or Pluto that isn't to the SSH port
tcpdump -vv src mars and not dst port 22
As you can see, you can build queries to find just about anything you need. The key is to first figure out precisely what you're looking for and then to build the syntax to isolate that specific type of traffic.
Grouping
Also keep in mind that when you're building complex queries you might have to group your options using single quotes. Single quotes are used in order to tell
tcpdump to ignore certain special characters -- in this case the "( )" brackets. This same technique can be used to group using other expressions such as host, port, net, etc. Take a look at the command below:
# Traffic that's from 10.0.2.4 AND destined for ports 3389 or 22(incorrect)
tcpdump src 10.0.2.4 and (dst port 3389 or 22)
If you tried to run this otherwise very useful command, you'd get an error because of the parenthesis. You can either fix this by escaping the parenthesis (putting a \ before each one), or by putting the entire command within single quotes:
# Traffic that's from 10.0.2.4 AND destined for ports 3389 or 22 (correct)
tcpdump 'src 10.0.2.4 and (dst port 3389 or 22)'
Advanced
You can also filter based on specific portions of a packet, as well as combine multiple conditions into groups. The former is useful when looking for only SYNs or RSTs, for example, and the latter for even more advanced traffic isolation.
[ Hint: An anagram for the TCP flags: Unskilled Attackers Pester Real SecurityFolk ]
Show me all URGENT (URG) packets...
# tcpdump 'tcp[13] & 32!=0'
Show me all ACKNOWLEDGE (ACK) packets...
# tcpdump 'tcp[13] & 16!=0'
Show me all PUSH (PSH) packets...
# tcpdump 'tcp[13] & 8!=0'
Show me all RESET (RST) packets...
# tcpdump 'tcp[13] & 4!=0'
Show me all SYNCHRONIZE (SYN) packets...
# tcpdump 'tcp[13] & 2!=0'
Show me all FINISH (FIN) packets...
# tcpdump 'tcp[13] & 1!=0'
Show me all SYNCHRONIZE/ACKNOWLEDGE (SYNACK) packets...
# tcpdump 'tcp[13]=18'
[ Note: Only the PSH, RST, SYN, and FIN flags are displayed in
tcpdump's flag field output. URGs and ACKs are displayed, but they are shown elsewhere in the output rather than in the flags field ]
Keep in mind the reasons these filters work. The filters above find these various packets because
tcp[13] looks at offset 13 in the TCP header, the number represents the location within the byte, and the !=0 means that the flag in question is set to 1, i.e. it's on.
As with most powerful tools, however, there are multiple ways to do things. The example below shows another way to capture packets with specific TCP flags set.
Capture TCP Flags Using the
tcpflags Option...
# tcpdump 'tcp[tcpflags] & & tcp-syn != 0'
Specialized Traffic
Finally, there are a few quick recipes you'll want to remember for catching specific and specialized traffic, such as IPv6 and malformed/likely-malicious packets.
IPv6 traffic
# tcpdump ip6
Packets with both the RST and SYN flags set (why?)
# tcpdump 'tcp[13] = 6'
Traffic with the 'Evil Bit' Set
# tcpdump 'ip[6] & 128 != 0'
Conclusion
Well, this primer should get you going strong, but the man pageshould always be handy for the most advanced and one-off usage scenarios. I truly hope this has been useful to you, and feel free tocontact me if you have any questions. ::
Recommended
- A
vimPrimer
http://danielmiessler.com/study/vim/ - A
tcpdumpPrimer
http://danielmiessler.com/study/tcpdump/ - An
lsofPrimer
http://danielmiessler.com/study/lsof/ - An Encoding Primer
http://danielmiessler.com/study/encoding/ - An HTTP Primer
http://danielmiessler.com/study/http/ - A Git Primer
http://danielmiessler.com/study/git/ - A Collection of Less Commonly Used Unix Commands
http://danielmiessler.com/blog/collection-of-less-commonly-used-unix-commands - 9 Enhancements to Shell and Vim Productivity
http://danielmiessler.com/writing/vulnerability_assessment_penetration_test/ - Information Security Interview Questions
http://danielmiessler.com/study/infosec_interview_questions/ - Top Content
http://danielmiessler.com/popular/
Cisco 2691 ADSL configuration
Cisco 2691 ADSL config (worked with PLDT )
vpdn-group pppoe request-dialin protocol pppoe ! interface ATM0/0 description PLDT ADSL no ip address no atm ilmi-keepalive dsl operating-mode auto hold-queue 224 in ! interface ATM0/0.1 point-to-point pvc 0/100 pppoe-client dial-pool-number 1 ! interface Dialer0 mtu 1492 ip addressip nat outside ip virtual-reassembly encapsulation ppp ip tcp adjust-mss 1436 dialer pool 1 no cdp enable ppp chap hostname <pldt pppoe username> ppp chap password 7 <pldt password> ppp pap sent-username <pldt pppoe username> password 0 <pldt password>
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