“Phishing in the middle of the stream”
Today’s threats to online banking
Candid Wüest
Security Response Engineer
November 2005
Agenda
Introduction
Local attacks
Protection methods used today
 Anti-Phishing tools
 SMS authentication
 Image verification
 PKI based solutions
Attacks against the weak points
Questions? & Answers!
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© 2005 Symantec Corporation.
Introduction
Online banking is popular
But many people fear that it is insecure
Wherever money is involved, bad guys appear trying to steal it!
Several known cases of online thefts:
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 June 2005 in Korea
Damage: ~ US$ 50’000
 February 2005 in USA
Damage: ~ US$ 90’000
© 2005 Symantec Corporation.
Evolution
Not only phishing emails with obscured links anymore
Targeted malware attacks are increasing
Trojans targeting financial services:
Increased in numbers:
20 variants in May 2003
>2000 variants in November 2005
PWSteal.Bancos.T (April 2005)
 Monitors 2764 different URLs
 On 59 different top-level domains
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© 2005 Symantec Corporation.
Local attacks – SSL
“But my session was SSL encrypted, I’m safe, right?”
Information is intercepted before it gets encrypted:
 Browser Helper Objects (BHO)
 Process injection
 DLL modules
 Layered service providers (LSP)
 Rootkits
 Screenshots (for virtual keyboards)
 Fake Pop-ups
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© 2005 Symantec Corporation.
General attack scenario
Assumptions: Malicious code running on the system.
Install rogue certification authority (CA)
 No SSL certification warnings
Redirect specific/all traffic to the attacker:
 Can be done with Hosts file, LSP, rootkits,…
 Attacker can send fake traffic to user
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© 2005 Symantec Corporation.
SMS challenge code
2-factor authentication using the mobile phone
The same applies to RSA tokens, iTANs, scratch lists
Logon to the web site:
Send username
Send OneTimePass
to registered mobile
Complete logon:
Send OneTimePass
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© 2005 Symantec Corporation.
Attacks on SMS challenge code
Logon to the fake
web site of attacker:
Send username
Send fake web answer
Logon to the real web
site using gathered
data: Send username
Send OneTimePass
to registered mobile
Complete the logon
on the fake web site:
Send OneTimePass
Send fake error answer
Complete the logon:
Send OneTimePass
ACCESS GRANTED
Countermeasure: Send transaction details in SMS for checking
Downside: Sends sensitive information in clear text message
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© 2005 Symantec Corporation.
Image verification
Personalize logon with custom image and personal text
Configuration saved on bank server
Only send your password if you see your image & text
John Doe
PassMark system
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© 2005 Symantec Corporation.
Image verification
Logon to the web site:
Send username
Send registered image & text
Verify image & text
Send password
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© 2005 Symantec Corporation.
Attacks on image verification
Logon to the faked
web site of attacker:
Send username
send a fake web site
with image & text
Verifies image & text
Send password
Send fake error answer
Logon to the real web
site using gathered
data: Send username
Send registered
image & text
Complete logon:
Send password
ACCESS GRANTED
Other attacks: Replay attack
Countermeasure: Not without serious changes
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© 2005 Symantec Corporation.
PKI based software solutions
Use cryptography to authenticate and protect the session
Example: WiKID open source solution
Initial setup: registering public key
PIN code for service (not saved on client)
Verification through different channel (phone)
Logon: send encrypted SVR{UserID,PIN}
Generate ticket: send encrypted USR{OneTimePass}
Complete logon: send OneTimePass
ACCESS GRANTED
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© 2005 Symantec Corporation.
Attacks on PKI based software solutions
Initial setup: registering public key
PIN code for service (not saved on client)
Verification through different channel (phone)
1.Logon: send encrypted SVR{UserID,PIN}
Generate ticket: send encrypted USR{OneTimePass1}
Send intercepted PIN
and private & public keys
2.Logon: send SVR{UserID,PIN}
send USR{OneTimePass2}
Countermeasure: Block hooking or boot clean OS (Knoppix)
Downside: Who protects anti-hooking tool? Ring0 Trojans?
Additional token (CD-ROM)
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© 2005 Symantec Corporation.
PKI based hardware token
Use external hardware tokens with PKI
 Smartcards with PKI application
 External reader with keypad and display (class 3)
 Connected to PC on USB or serial cable
HBCI; already in use for years in Germany
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© 2005 Symantec Corporation.
PKI based hardware token
Unlock smartcard with PIN
Verify Java Applet signature
request logon web page
Send signed Java Applet
Initiate mutual SSL
Send username
Enter challenge CH1
Display response RS1
Send challenge CH1
Enter response RS1
Enter transaction
Display & sign (T1)
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send transaction & (T1)
© 2005 Symantec Corporation.
Attacks on PKI based hardware token?
Transaction can not be manipulated, as the
transaction is signed on external hardware
Signing is only accessible from the external
reader and can not be triggered by a Trojan
Downside:
- Not easy portable (Internet café)
- More expensive then other solution
- Not so convenient for end user
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© 2005 Symantec Corporation.
Summary
Malware targeting financial services exists and increases in
number. Why? There is money involved!
Software running on compromised systems can be targeted
and must protect itself wisely or it will be rendered useless.
Most solutions today can solve the phishing problem but not
man-in-the-middle attacks with Trojan horses.
There are possibilities to protect, so don’t give up the fight!
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© 2005 Symantec Corporation.
Questions?
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© 2005 Symantec Corporation.
Thank you for your attention !
Candid Wüest
candid_wueest@symantec.com