Email Tracing COEN 152 / 252 Computer Forensics Thomas Schwarz, S.J. 2006
Email Investigations: Overview • Email has become a primary means of communication. • Email can easily be forged. • Email can be abused • Spam • Aid in committing a crime … • Threatening email, …
Email Investigations: Overview • Email evidence: • Is in the email itself • Header • Contents • In logs: • Left behind as the email travels from sender to recipient. • Law enforcement uses subpoenas to follow the trace. • System admins have some logs under their control. • Notice: All fakemailing that you will be learning can be easily traced.
Email Fundamentals • Email travels from originating computer to the receiving computer through email servers. • All email servers add to the header. • Use important internet services to interpret and verify data in a header.
Email Fundamentals • Typical path of an email message: Mail Server Client Mail Server Client Mail Server
Internet Basics • IP Address – IPv4 • IP Address – IPv6 • IP Address Types • Hostnames & DNS • Email Routing • Resources
Internet Basics:IP Address – IPv4 • Dominant standard for addressing • 32 bit address space • 4 bytes 232 or 4.3B addresses • Typical representation is 4 octets • Ranges from 0.0.0.0 to 255.255.255.255 • E.g. – 22.214.171.124 • Integer representation is 3,518,986,822 • Almost a 30 year old standard • >90% of all IPv4 addresses allocated
Internet Basics:IP Address – IPv6 • Next Generation of Internet addressing • 128 bit address space • 16 bytes 2128 or 3.4×1038 • 340 trillion trillion trillion • 340,000,000,000,000,000,000,000,000,000,000 000,000 • Represented as 8 hexadecimal numbers • Ranges from 0:0:0:0:0:0:0:0 to FFFF:FFFF:FFFF:FFFF: FFFF:FFFF:FFFF:FFFF • Examples (with shorthand notation) • 2001:db8:1f70::999:de8:7648:6e8 • FF3E:40:2001:dead:beef:cafe:1234:5678 • 10+ years of deployment, but still maturing
Internet Basics:IP Address Types • Public / Private • Some addresses are public or externally visible • Others are private or internal to an organization • RFC 3330 defines these ranges and their purpose • The most commonly seen “private” addresses • 10.0.0.0 – 10.255.255.255 • 172.16.0.0 – 172.31.255.255 • 192.168.0.0 – 192.168.255.255 • Private addresses are unroutable externally • Proxies • Anonymizers, Satellites, International and Regional
Internet Basics:IP Address Types (cont) • Static / Dynamic addresses • Some IP addresses are statically assigned to a single computer • Typically infrastructure and/or servers • Some are shared by multiple computers using NAT or DHCP within a local organization • Many organizations use Network Address Translation (NAT) • NAT boxes – single externally visible IP address • Incoming packet examined and routed according to the source address and port number • Forwarded to an internal, private IP address
Internet Basics:Hostnames & DNS • DNS is the Domain Name System • Translates between human friendly host/domain names (e.g. www.yahoo.com) and machine friendly IP addresses • Forward DNS Lookup • “dig www.yahoo.com” or “nslookup www.yahoo.com” • www.yahoo.com 126.96.36.199 • Reverse DNS Lookup • “dig –x 188.8.131.52” or “nslookup 184.108.40.206” • 220.127.116.11 www.yahoo.com
Internet Basics:Hostnames & DNS • DNS Overview • Conceptually a cached hierarchy of host/domain name assignments and IP addresses • Each node is a name server • Requests originate local to the user and escalate “up” only as far as necessary, then “down” as soon as possible – tree traversal • DNS Root servers are at the “top”
Internet Basics:Hostnames & DNS • DNS Overview (continued) • Searches start with the “local host” file • Missing or stale entries escalate up • Local name server is the first stop, then usually the local ISP’s up through to the Root Name Servers as necessary • Once an authoritative, responsible name server is found, the search is downward focused until the specific machine name/address is found.
Internet Basics:Hostnames & DNS • DNS Overview (continued) • Complete escalation is usually not required, as caching is extensively used • The local “host file” file can be altered • Can be used to block pop-ups and bad websites • E.g., Spybot uses this as a preventative technique • Malware can use this “feature” as well • Local name servers can/could be injected with malicious data • See the “Hillary for Senate” case
Internet Basics:Resources • Internet Assigned Numbers Authority • Responsible for the global coordination of the DNS Root, IP addressing, and other Internet protocol resources • Managed resources include • Port Numbers • Autonomous Systems Numbers • Top Level Domains (TLDs) • www.iana.org
Internet Basics:Resources (cont) • Regional Internet Registries • Five regions • APNIC – Asia and the Pacific region • ARIN – North America (the first registry, legacy entries) • LACNIC – Latin American and Caribbean • RIPE – Europe • AfriNIC – Africa • Regionally allocates IP addresses to orgs • Each provides IP address “whois” services • i.e. who is responsible for an IP address
Internet Basics:Resources (cont) • IP address top level allocations and registry assignments • www.iana.org/assignments/ipv4-address-space • whois • Regional Internet registries definitive source • DNSStuff - http://www.dnsstuff.com alternative • whois provides owner, location, contact info • Geolocation • Maxmind - www.maxmind.com
Internet Basics:Resources (cont) • Hostname lookups • dig, replacing nslookup • “dig www.scu.edu” • “dig –x 18.104.22.168” (reverse lookup) • “traceroute” (tracert) • Great for verifying general location and possible affiliations • Web versions are available from around the world
Email Fundamentals: Important Services • Domain Name System (DNS) translates between domain names and IP address. • MX records (http://en.wikipedia.org/wiki/MX_record) in the DNS database specify the host’s or domains mail exchanger • Can have multiple MX records, with priority attached: • Email to email@example.com will then be sent to firstname.lastname@example.org. • If that site is down, then it will be sent to email@example.com. • The mailer at both sites needs also be set up to accept the messages. MX 10 cse MX 100 mailhost.soe.uscs.edu
Email Protocols: • A mail server stores incoming mail and distributes it to the appropriate mail box. • Behavior afterwards depends on type of protocol. • Accordingly, investigation needs to be done at server or at the workstation.
Email Protocols: • Email program such as Outlook or Groupwise are a client application. • Needs to interact with an email server: • Post Office Protocol (POP) • Internet Message Access Protocol (IMAP) • Microsoft’s Mail API (MAPI) • Web-based email uses a web-page as an interface with an email server.
Email Protocols: SMTP • Neither IMAP or POP are involved relaying messages between servers. • Simple Mail Transfer Protocol: SMTP • Easy. • Has several additions. • Can be spoofed: • By using an unsecured or undersecured email server. • By setting up your own smtp server.
Email Protocols: SMTPHow to spoof email telnet endor.engr.scu.edu 25 220 endor.engr.scu.edu ESMTP Sendmail 8.13.5/8.13.5; Wed, 28 Dec 2005 14:58:49 - 0800 helo 22.214.171.124 250 server8.engr.scu.edu Hello dhcp-19-198.engr.scu.edu [126.96.36.199], please d to meet you mail from: firstname.lastname@example.org 250 2.1.0 email@example.com... Sender ok rcpt to: firstname.lastname@example.org 250 2.1.5 email@example.com... Recipient ok data 354 Enter mail, end with "." on a line by itself This is a spoofed message. . 250 2.0.0 jBSMwnTd023057 Message accepted for delivery quit 221 2.0.0 endor.engr.scu.edu closing connection
Email Protocols: SMTP Return-path: <firstname.lastname@example.org> Received: from MGW2.scu.edu [188.8.131.52] by gwcl-22.scu.edu; Wed, 28 Dec 2005 15:00:29 -0800 Received: from endor.engr.scu.edu (unverified [184.108.40.206]) by MGW2.scu.edu (Vircom SMTPRS 4.2.425.10) with ESMTP id <C0066443608@MGW2.scu.edu> for <email@example.com>; Wed, 28 Dec 2005 15:00:29 -0800 X-Modus-BlackList: 220.127.116.11=OK;firstname.lastname@example.org=OK X-Modus-Trusted: 18.104.22.168=NO Received: from bobadilla.engr.scu.edu (bobadilla.engr.scu.edu [22.214.171.124]) by endor.engr.scu.edu (8.13.5/8.13.5) with SMTP id jBSMwnTd023057 for email@example.com; Wed, 28 Dec 2005 15:00:54 -0800 Date: Wed, 28 Dec 2005 14:58:49 -0800 From: JoAnne Holliday <firstname.lastname@example.org> Message-Id: <200512282300.jBSMwnTd023057@endor.engr.scu.edu> this is a spoofed message. This looks very convincing. Only hint: received line gives the name of my machine. If I were to use a machine without a fixed IP, then you can determine the DHCP address from the DHCP logs.
Email Protocols: SMTPHow to spoof email • Endor will only relay messages from machines that have properly authenticated themselves within the last five minutes. • Subject lines etc. are part of the data segment. However, any misspelling will put them into the body of the message.
Email Protocols: SMTPHow to spoof email telnet endor.engr.scu.edu 25 220 endor.engr.scu.edu ESMTP Sendmail 8.13.5/8.13.5; Wed, 28 Dec 2005 15:36:13 - 0800 mail from: email@example.com 250 2.1.0 firstname.lastname@example.org... Sender ok rcpt to: email@example.com 250 2.1.5 firstname.lastname@example.org... Recipient ok data 354 Enter mail, end with "." on a line by itself Date: 23 Dec 05 11:22:33 From: email@example.com To: firstname.lastname@example.org Subject: Congrats You are hrby appointed the next president of Santa Clara University, effectively immediately. Best, Paul . 250 2.0.0 jBSNaDlu023813 Message accepted for delivery quit
Email Protocols: SMTPHow to spoof email • Unix • Use sendmail • %usr/lib/sendmail –t –f HolyFather@vatican.va < test_message
Email Protocols: SMTP • Things are even easier with Windows XP. • Turn on the SMTP service that each WinXP machine runs. • Create a file that follows the SMTP protocol. • Place the file in Inetpub/mailroot/Pickup
Email Protocols: SMTP To: email@example.com From: HolyFather@vatican.va This is a spoofed message. From HolyFather@vatican.va Tue Dec 23 17:25:50 2003 Return-Path: <HolyFather@vatican.va> Received: from Xavier (dhcp-19-226.engr.scu.edu [126.96.36.199]) by server4.engr.scu.edu (8.12.10/8.12.10) with ESMTP id hBO1Plpv027244 for <firstname.lastname@example.org>; Tue, 23 Dec 2003 17:25:50 -0800 Received: from mail pickup service by Xavier with Microsoft SMTPSVC; Tue, 23 Dec 2003 17:25:33 -0800 To: email@example.com From: HolyFather@vatican.va Message-ID: <XAVIERZRTHEQXHcJcKJ00000001@Xavier> X-OriginalArrivalTime: 24 Dec 2003 01:25:33.0942 (UTC) FILETIME=[D3B56160:01C3C9 BC] Date: 23 Dec 2003 17:25:33 -0800 X-Spam-Checker-Version: SpamAssassin 2.60-rc3 (1.202-2003-08-29-exp) on server4.engr.scu.edu X-Spam-Level: X-Spam-Status: No, hits=0.3 required=5.0 tests=NO_REAL_NAME autolearn=no version=2.60-rc3 This is a spoofed message.
Email Protocols: SMTP • SMTP Headers: • Each mail-server adds to headers. • Additions are being made at the top of the list. • Therefore, read the header from the bottom. • To read headers, you usually have to enable them in your mail client.
SMTP Headers To enable headers: • Eudora: • Use the Blah Blah Blah button • Hotmail: • Options Preferences Message Headers. • Juno: • Options Show Headers • MS Outlook: • Select message and go to options. • Yahoo!: • Mail Options General Preferences Show all headers. • Groupwise: • Message itself is “attached” to each email. You need to look at it.
SMTP Headers • Headers consists of header fields • Originator fields • from, sender, reply-to • Destination address fields • To, cc, bcc • Identification Fields • Message-ID-field is optional, but extremely important for tracing emails through email server logs. • Informational Fields • Subject, comments, keywords • Resent Fields • Resent fields are strictly speaking optional, but luckily, most servers add them. • Resent-date, resent-from, resent-sender, resent-to, resent-cc, resent-bcc, resent-msg-id
SMTP Headers • Trace Fields • Core of email tracing. • Regulated in RFC2821. • When a SMTP server receives a message for delivery or forwarding, it MUST insert trace information at the beginning of the header.
SMTP Headers • The FROM field, which must be supplied in an SMTP environment, should contain both (1) the name of the source host as presented in the EHLO command and (2) an address literal containing the IP address of the source, determined from the TCP connection. • The ID field may contain an "@" as suggested in RFC 822, but this is not required. • The FOR field MAY contain a list of <path> entries when multiple RCPT commands have been given. • A server making a final delivery inserts a return-path line.
SMTP Header • Spotting spoofed messages • Contents usually gives a hint. • Each SMTP server application adds a different set of headers or structures them in a different way. • A good investigator knows these formats. • Use internet services in order to verify header data. • However, some companies can outsource email or use internal IP addresses. • Look for breaks / discrepancies in the “Received” lines.
SMTP Header • Investigation of spoofed messages • Verify all IP addresses • Keeping in mind that some addresses might be internal addresses. • Make a time-line of events. • Change times to universal standard time. • Look for strange behavior. • Keep clock drift in mind. • Additonal Info: http://www.uic.edu/depts/accc/newsletter/adn29/headers.html
Server Logs • E-mail logs usually identify email messages by: • Account received • IP address from which they were sent. • Time and date (beware of clock drift) • IP addresses
Server Logs Dec 31 18:26:15 endor sendmail: k012OV1i030597: firstname.lastname@example.org, size=147, class=0, nrcpts=1, msgid=<200601010225.k012OV1i030597@endor.engr.scu.edu>, proto=SMTP, daemon=MTA, relay=c-24-12-227-211.hsd1.il.comcast.net [188.8.131.52] Dec 31 18:26:15 endor spamd: spamd: connection from localhost [127.0.0.1] at port 42865 Dec 31 18:26:15 endor spamd: spamd: setuid to tschwarz succeeded Dec 31 18:26:15 endor spamd: spamd: processing message <200601010225.k012OV1i030597@endor.engr.scu.edu> for tschwarz:1875 Dec 31 18:26:15 endor spamd: spamd: clean message (4.6/5.0) for tschwarz:1875 in 0.2 seconds, 525 bytes. Dec 31 18:26:15 endor spamd: spamd: result: . 4 - MSGID_FROM_MTA_ID,RCVD_IN_NJABL_DUL,RCVD_IN_SORBS_DUL scantime=0.2,size=525,user=tschwarz,uid=1875,required_score=5.0,rhost=localhost,raddr=127.0.0.1,rport=42865,mid=<200601010225.k012OV1i030597@endor.engr.scu.edu>,autolearn=no Dec 31 18:26:15 endor spamd: prefork: child states: II Dec 31 18:26:15 endor sendmail: k012OV1i030597: email@example.com, delay=00:01:02, xdelay=00:00:00, mailer=local, pri=30464, dsn=2.0.0, stat=Sent Sample log entry at endor.
Server Logs • Many servers keep copies of emails. • Most servers purge logs. • Law-enforcement: • Vast majority of companies are very cooperative. • Don’t wait for the subpoena, instead give system administrator a heads-up of a coming subpoena. • Company: • Local sys-ad needs early warning. • Getting logs at other places can be dicey.
Unix Sendmail • Configuration file /etc/sendmail.cf and /etc/syslog.conf • Gives location of various logs and their rules. • maillog (often at /var/log/maillog) • Logs SMTP communications • Logs POP3 events • You can always use: locate *.log to find log files.
Techniques • Investigating email for forgery • Evidentiary material is • Directly in header • Indirectly in formatting headers • Timestamps • Header Trace Resource • http://www.ip-adress.com/trace_email/
Techniques • Header Investigation • Lookup all host names and IP addresses • Check for inconsistencies • Be aware of • internal IP addresses • web hosting company • Generate Timeline • Be aware of • clock drift, • delays, • time zone differences