A High PHP Memory Limit in Joomla = An Invitation for DoS Attacks

Occasionally, Joomla administrators face the infamous allowed memory size error which forces them to increase the memory_limit value in the global php.ini or in a local .user.ini file by adding the following line:


The above code will increase the memory limit to 256 megabytes, which is more than ample for any Joomla website out there. Now, the thing is, the absolute majority of the times, Joomla administrators increase the memory limit to allow an occasional usage of a certain Joomla functionality, such as updating the Joomla website or installing an extension. Once the update is done or the extension is installed, then there is no need for the high PHP memory limit anymore.

Unfortunately, most Joomla administrators do not revert back the changes they did to the PHP memory limit – mainly because they think it’s better this way (it did fix the problem – didn’t it?). But it’s not – in fact, a high memory limit makes a DoS (Denial of Service) attack easier and much more dangerous. Let us explain…

The PHP memory limit defines how much memory each PHP page is allowed to consume – so if, for instance, you have a memory limit of 256 megabytes, then, assuming a worst case scenario, merely 8 simultaneous page views can take up 2 GB of your server’s RAM. So, if an attacker knows of a page on your website that consumes a lot of memory, then the attacker can simply release some bots on that page and quickly bring your server to its knees by exhausting all of its (the server’s) memory.

But what is an ideal PHP memory limit?

Ideally, a page on a Joomla website should not consume more than 32 MB of memory (and that’s very generous). If you find that on some pages (with the exception of the core update page) your Joomla website needs more memory than that, then you might be a victim of a bad Joomla programmer. In that case, you will need some Joomla experts, such as (ahem) us, to address this issue for you. Just contact us and and we’ll fix the problem for you in no time and for a very reasonable price!

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