In the unlikely event of your site getting reinfected after our clean up, just open a new malware removal request ticket and explain what happened. Our team will happily check out what is going on.
Most of the reinfection cases we deal with on a daily basis are either caused by out-dated software or password compromise.
We also see lots of cases where the website is sharing hosting space with a number of other websites.
This puts your protected site at risk of cross contamination. More info here.
In those cases, we recommend migrating the website to its own, isolated hosting environment or upgrading your Sucuri Plan to cover all the websites in the server.
Last but not least, we highly recommend checking these steps to keep your website in a clean state.