Transcript Why is Security So Hard?

Why is Internet Security
So Hard?
Dr. Stephen Kent
Chief Scientist- Information Security
Internet Security
Security for the Internet includes both security for
network operations and security for network users
The former is usually the purview of ISPs, the
latter is a shared responsibility among users, ISPs,
and vendors
For network users, there is a need to secure
information on computers and in transit across the
Internet
This presentation focuses on security for Internet
users
What is Security?
ISO 7498-2 defines five security services
Confidentiality (secrecy)
 Authentication (identify verification)
 Integrity
 Access control
 Non-repudiation (not “taking back” what one “said”)

Users also would likely include
Preventing spam
 Preventing denial of service
 Privacy
…

Information Security Disciplines
Physical security
Procedural security
Personnel security
Compromising emanations security
Operating system security
Communications security
a failure in any of these areas can
undermine the security of a system
Security Terminology
Vulnerabilities

security flaws in systems
Attacks

means of exploiting vulnerabilities
Countermeasures

technical or procedural means of addressing
vulnerabilities or thwarting specific attacks
Threats

motivated adversaries capable of mounting attacks
which exploit vulnerabilities
Adversaries (The Bad Guys)
Hackers
Disgruntled employees
Industrial spies
Terrorists
Special interest groups
Journalists
Real spies
Criminals (organized or otherwise)
Adversary Characteristics
Capabilities
Network wiretapping
 Remote attacks against operating systems or
applications
 “Social engineering” (e.g., SPAM)
 Physical attacks
 Personnel subversion

Resources
Personnel
 Technology
 Funds

Aversion to detection
Vulnerabilities
The simple characterization of our problem is the
existence of vulnerabilities in products
We face a two sorts of vulnerability problems:
Known vulnerabilities
 Unknown vulnerabilities

For known vulnerabilities we can deploy specific
countermeasures
For unknown vulnerabilities, at best we try to
prevent/detect behavior that might be exploiting
these vulnerabilities
Sources of Vulnerabilities
Design flaws
operating system & application vulnerabilities
 protocol design vulnerabilities

Implementation flaws
programming errors
 undocumented system & application “features”

Mismanagement
unintended and/or residual authorizations
 failure to deploy security bug fixes

Security Continuum
There are no perfect, secure systems
Systems are "adequately secure" only relative to a
perceived threat
Absence of obvious insecurities is not a good
indication that a system is adequately secure
Risk analysis, if properly performed, provides a
methodology for identifying what constitutes
adequate security
The Threshold Effect
Once a technical attack against a security
technology has been "debugged" it can be
executed by a wide range of (inexperienced)
attackers
A technical attack that can be effected using
inexpensive hardware or software is especially
easy to transfer from sophisticated attackers to
amateurs
Thus it is dangerous to dismiss an attack as "too
complex or too technical" because the perceived
attackers do not possess the technical capability to
mount the attack
Why are the Bad Guys Winning?
Most vendor software has poor security
characteristics
Too complex
 Badly designed
 Buggy

Most users are sloppy
Don’t install the latest patches
 Easily tricked (social engineering)
 Poor password choices, password reuse, …

Hackers value their time at 0, but user have other
priorities in life!
Common Defense Strategies
Firewalls
Intrusion Detection Systems
Anti-virus technology (in hosts and in mail
gateways)
Anti-spam technology (in hosts and in mail
gateways)
Periodic penetration testing (enterprise nets)
Centralized patch management (enterprise nets)
 Anti-DOS mechanisms (ISPs)
Firewalls
Recently renamed Intrusion Prevention Devices
(IPDs), probably to help sell more of them :-)
The term covers a wide range of technologies,
from simple, stateless packet filtering, to
application-specific devices
At the low end, these offer minimal protection
against most adversaries
At the high end they are expensive and often
interact badly with new applications
In all cases, management of the firewall rule sets
is complex, time consuming, and thus imperfect
Intrusion Detection Systems (IDSs)
 An IDS attempts to:



Detect behavior that exploits known vulnerabilities
Detect behavior that might exploit some class of unknown
vulnerabilities
Detect behavior that might be a precursor to an attack
 IDS may attempt to:



Detect signatures of known attacks
Detect anomalous behavior
Do both
 IDS’s tend to work poorly, because of the ambiguities
associated with attempts to deal with unknown attacks or
to define “normal” behavior
 False positives (incorrect flagging of traffic as “evil” is
common, and makes these systems hard to use
Anti-virus Systems
These attempt to detect viruses (and worms),
typically distributed via e-mail attachments or
other forms of file transfer
Usually they are signature based, which means
they know only about previously-detected viruses
A network manager or user has to acquire
signature list updates periodically, or become
vulnerable to newer viruses
These can be effective if properly managed, but
people are sloppy, and virus writers are prolific
Anti-spam Technology
The problem with spam is that it is impossible to
distinguish from legitimate mail, in the worst case
Some anti-spam technology works on signatures,
like anti-virus technology, but it is not very
effective because spam generation software does
not focus on software vulnerabilities, like viruses
Some anti-spam technology is based on Baysean
filters (probabilistic measures), but it too is subject
to false positive/false negative tuning problems
Spam is of value to its senders primarily because
users are greedy or naïve; solving this is NOT a
technical problem
Penetration Testing
This is an approach used by many enterprises, but
rarely by individual users
At the low end it is automated, mostly a patch
check on end systems and a firewall filer rules
check
At the high end one pays “experts” to try to break
into your system(s)
The low end is useful as a form of external
checking re good housekeeping
The high end is very expensive
Centralized Patch Management
The notion here is to enable an IT organization to
check the status of end systems and to patch them
before the systems are successfully attacked
Vendors like Cisco and Microsoft offer this as a
service, part of “admission control” to a LAN
This is another form of “good housekeeping”
checking, on a more frequent basis
It is analogous to low end penetration testing, a
form of centrally managed anti-virus updating
BUT, an already-compromised system can avoid
detection if the attacker is clever
Anti-DoS Technology
 Denial of service attacks seek to make resources
unavailable, typically through overloading network access
lines with lots of traffic
 The problem is that it is hard to tell good traffic from bad
traffic out in the Internet (vs. at an end system)
 Some systems try to look at traffic flows and discard
packets if the flow to a given destination is “too high”
BUT, good traffic is often discarded as well as bad!
 We know that some DoS hackers have thousands of
“zombie” systems available to them, dispersed over the
Internet, to launch attacks, which makes it almost
impossible to counter such attacks without causing
problems for legitimate users as well
Abstraction and Attacks
One strategy for an adversary is to attack below
the layer of abstraction at which security measures
are defined, or via ill-defined interfaces
Complex applications and operating systems like
Windows have many ill-defined interfaces
Security measures implemented in applications (or
middleware) embody high levels of abstraction
The trend is to create more opportunities for an
attacker as we use more complex, high level
application development environments, e.g., web
services
Security in Products:
Functionality vs. Assurance
Security functions: usually visible, securityrelevant features that provide the means by which
security is invoked and managed
Security assurance: often invisible means by
which one develops confidence in the correct
operation of security features
Many products now advertise lots of security
functions (because today, security sells), but the
products offer little or no assurance!
Security Assurance
Product security assurance techniques
penetration testing
 detailed code review
 use of formal specifications
 security evaluation criteria

Unfortunately, these techniques are either very
expensive or very haphazard
As a result, we have few products for which we
have a good idea of their security quality
Security & Privacy: A Quick Look
Security
Accountability
 Uniform identification
 Extensive auditing
 Correlation of audit data
 Centralized management
 Mediated access to all
data

Privacy
Anonymity
 Use of diverse identifiers
 Limited data collection
 No sharing of records
 Distributed autonomy
 Mediated access to
records that affect
privacy

Security and privacy need not be in conflict,
but it takes a lot of effort to balance the two
Conclusions
Internet security is hard because:
Its hard to counter unknown vulnerabilities in products
 Even security products themselves often have unknown
vulnerabilities
 The utility of an IDS is limited by feature rich
environments
 Most CIOs can’t even track all the systems in their nets
 There is no methodology for designing a secure system
from secure components (and we have few secure
components anyway)
 Abstraction favors the adversary
 Some problems (e.g., spam) are not technical in nature
 People are sloppy, greedy, and sometimes naïve

Questions