A simple and easy way to avoid unprofitable traffic consistently is to use the Global Blacklist tool.

With this feature, you can quickly block all non-yielding traffic sources at the account level.

Once you set up your account’s Global Blacklist and include all unqualified sources in it, there's no need to block those sources again for each campaign.

Here's how to set it up:

1. Click on the Account Settings tab

2. Select Blacklist tab

3. In the dialog box, insert all sources you want to block traffic from (Insert each source on a separate line). 

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* If you whitelist a source that appears on your global blacklist, please note: Whitelisting at the campaign level overrides your global blacklist.
This means that only this specific campaign will receive traffic from that source.