INFS2052 lecture 4.3

Java Technology ctd. and

Other Active Content Technologies

References

Garfinkel and Spafford, Web Security and Commerce
chapter 3 Java and Javascript (security)

Denial of Service attacks

Java security is not proof against denial of service attacks.

Denial of service

means the excessive consumption of resources: screen, CPU, memory, processes, interrupt handlers, socket connections, etc.
by an offending process
to the exclusion of other (desirable) process's use of these limited computing resources.

Some use of resources is intended for any process.. how much is excessive?

A faulty or malicious applet can run away with resources doing apparently nothing or trivial things.

flood of method calls tie up nearly all CPU for little effect
allocation of larger and larger objects can tie up all of memory, thrash virtual memory, exclude activity from the rest of system
popping up multiple screen windows - each is often very expensive operation and high priority

Denial of service possibility is serious in Java etc. because authors did not consider this form of attack: the JVM interpreter is not built to exclude it;

PC operating systems are not as independently robust as old batch or multi-user mainframe systems.

Solutions:

not the browser security model: can't simply block operations, can't tell in general whether user wants this effect or not, can't compare to other use of resources in system
a good operating system, a good browser:
will be fair in use of resources between threads and processes, so that even a runaway process cannot lock out others
- may include more checking of excess activity (limit memory space used etc.)- some time penalty even if no offence

- will allow the user back into control.

Java security - summing up

security obtained by enbedding a security policy into the runtime environment in the elements:

security manager
class loader
trust certificates

No theoretical base for the security model:
not as secure as encryption systems with mathematical/computational complexity theory and years of open published literature examination as basis for belief in security

but may be strengthened in future with automated proof systems on applets
[ANU research]

Vulnerabilities

within Java technologies

outside J. technology: old methods still apply:
spoofing etc, Trojan horses, viruses, email, user's own actions

Advantage of Java model is that greater level of simple security comes with the same effort (running in sandbox vs running in the open)

No silver bullets:

web-based systems must be openly accessable to many new opportunities of applications (change or wither away!) in information dissemination, computer mediated communications, distributed applications, electronic commerce...

always opportunites to spam, skim, scam

always a dynamic balance between social desires for privacy and open information, equal access rights.