Ive been a fan of shared hosting as a cost-efficient solution for most Web sites, but you pay a price for saving that money. Im not as much of a fan as I used to be.
In a way, its like taking a bath with strangers. You probably save a lot of water, but you dont know whats in there besides the soap. A well-designed and -managed operating system and other system software can attempt to protect applications and users from each other, but things do go wrong at times.
Consider what happens when an attacker goes after one of the other sites on your shared server. Vulnerabilities such as this MySQL Password Handler Buffer Overflow Vulnerability or this PHP wordwrap() Heap Corruption Vulnerability occur. If the attacker gains control of the server or the database, youre all just as vulnerable.
And it may not be an outsider. It could be one of the other hosting customers. If the hosting admin and other customers arent attentive, the offending party might even get away with it.
Shared hosting has the potential to be a great thing for both host and customer alike. Because the host can run literally thousands of low-volume sites on a single box for Web hosting (they need another box for mail hosting), it can be enormously profitable even when the sites are very inexpensive. There are a number of mature “control panels” available to hosts, and many write their own, to let customers manage their own sites. If things go well, it should be nearly pure profit.
I guess dedicated hosting must be even more profitable, since hosting services seem to push it far more than the cheap shared plans. I suspect there are a lot of dedicated hosting users out there paying $150 a month for needs that would be served by a $20-a-month shared plan.
Mike Prettejohn of Internet research firm Netcraft Ltd., which follows the hosting market carefully, said he thinks “strongly themed shared hosting—e.g. the Yahoo storefronts”—are the best type of shared hosting. They define a rigid but easy-to-use environment for the customer, limiting the damage the customer can do, accidentally or otherwise, and they scale brilliantly for the hosting company.
Generic shared-hosting accounts, on the other hand—the ones with access to Perl and PHP and (shudder!) shell accounts—are a potential disaster. Its very easy for one customer to DoS (denial of service) all of the others with a badly written program. And you know how youll often read about a vulnerability in Linux, such as this one, but its not so big a deal because only local users can exploit it, not remote users? Those shell accounts make the users local. (Good management can prevent those users from uploading and executing arbitrary and exploitative code, but good management isnt built into the operating system.)
And then there are the external DoS attacks. Ive read reports indicating that general DoS attacks against hosting services are up, so if your sites are in the wrong IP range, you get to suffer along with everyone else.
Next Page: Blocked mail can be one form of death by association.
Death by Assocation
Mail servers arent immune to “death by association.” I once had a shared hosting account and woke one day to find that my mail from that domain was blocked by one of the major RBLs (Realtime Blackhole Lists), such as Mail Abuse Prevention System. Some digging revealed that this RBL blocked mail servers by IP address, and I was on a shared mail server. In all likelihood, some other domain on the same server had been spamming, but I paid the price all the same.
Security issues for hosted domains havent been covered enough by the media. I began to touch on them and how they are more common than is generally thought in a recent column on DDoS (distributed-denial-of-service) attacks.
But the implications for the industry are significant. I agree with Peter Pathos, president of The Planet Internet Services Inc. of Dallas. In a recent interview, Pathos said security issues would be the death of the “mom-and-pop” hosting industry and that “only those larger hosting companies focused on security will succeed.”
Pathos went on to describe some of the products and practices his company uses to secure its customer sites. Its all good, but most of it protects the inside from whats outside. Once something comes into a server, say by a trusted customer, theres only so far that operating-system hardening can take you.
And not every hosting service spends all of the money on security that The Planet does. As a general matter, you should consider your own site, even one on a dedicated server, more vulnerable to attacks from other sites in the same data center than from outside. You know how in the movies the bank robbers rent the basement next door and break in at night? If you want to attack an Internet site, maybe even an Internet bank, rent a logically nearby server.
But nothings more nearby than another site on a shared server. If security is really important, you really ought to get yourself a dedicated server. If youre scared off by the money it costs, security probably isnt as important to you as you think.
Security Center Editor Larry Seltzer has worked in and written about the computer industry since 1983.
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