Feeds

Denial, exposure and online security

Five top tips

Top 5 reasons to deploy VMware with Tegile

Web applications have huge attack surfaces. Most sites have hundreds of URLs, and each function has plenty of parameters, form fields, cookies, and headers for attackers to play with.

One simple way to make your web application more secure is to minimize your attack surface. Let's look at five simple ways to do this.

Tighten up your URL space

The first step is to lock down your webserver, application server, application configuration, and code tree to be sure that you're not supporting any URLs that you didn't expect.

You should also check your application for functions, backup files, temporary files, and test code that wasn't intentionally deployed. Just because they're not linked in the user interface, doesn't mean an attacker can't find and exploit them. Also, be sure you're not supporting all file extensions - just the specific ones you expect.

Ditch those hidden fields

Hidden fields are form values that aren't displayed to the user. When the user submits a form, the hidden fields are submitted just like any other form field. Attackers can easily change hidden field values to anything they want with browser tools like TamperData or WebDeveloper. Hidden fields are frequently quite vulnerable to attack because they're often overlooked when implementing validation.

You could use normal input validation techniques to check the hidden field, but the best way to check is to do a direct comparison with the value that you just set in the web page. Of course, if you can do this, there's really no point in having the hidden fields at all, so consider just getting rid of them and reducing your attack surface.

Don't expose your privates

Most applications use parameters or form fields that reference data on the server by its name or ID. Attackers love to try to access unauthorized data by tampering with these "direct" references. For example, imagine a URL that references a file on the server:

http://www.example.com/banking/fetchReport?fn=03102008.xl

Attackers will immediately attempt to manipulate the filename to access other files on the host. If the code takes the "fn" parameter and appends it to a filepath, the attacker might try sending the following to gain access to the host's password file:

 "?fn=../../../../etc/password%00"

The %00 at the end of the URL will be decoded by the container into a null byte that terminates the string, leaving only the attackers path in the parameter. There are hundreds of attack variants, so don't try to filter out attacks.

Choosing a cloud hosting partner with confidence

More from The Register

next story
Microsoft to bake Skype into IE, without plugins
Redmond thinks the Object Real-Time Communications API for WebRTC is ready to roll
Mozilla: Spidermonkey ATE Apple's JavaScriptCore, THRASHED Google V8
Moz man claims the win on rivals' own benchmarks
Microsoft promises Windows 10 will mean two-factor auth for all
Sneak peek at security features Redmond's baking into new OS
FTDI yanks chip-bricking driver from Windows Update, vows to fight on
Next driver to battle fake chips with 'non-invasive' methods
DEATH by PowerPoint: Microsoft warns of 0-day attack hidden in slides
Might put out patch in update, might chuck it out sooner
Ubuntu 14.10 tries pulling a Steve Ballmer on cloudy offerings
Oi, Windows, centOS and openSUSE – behave, we're all friends here
Apple's OS X Yosemite slurps UNSAVED docs into iCloud
Docs, email contacts... shhhlooop, up it goes
Was ist das? Eine neue Suse Linux Enterprise? Ausgezeichnet!
Version 12 first major-number Suse release since 2009
prev story

Whitepapers

Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.
Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.
Getting ahead of the compliance curve
Learn about new services that make it easy to discover and manage certificates across the enterprise and how to get ahead of the compliance curve.