Meltdown and Spectre are hardware vulnerabilities. They actually reside in your processor and are interested in sensitive information.
Meltdown is specific for Intel Processors.
Spectre is for processors other than Intel (not Intel).
- Meltdown bypasses the 'protection mode' that is present when you want to access sensitive data that is stored in your processor.
The attack imitates the role of a normal user that is accessing the
data. The reason sandbox is useless is because the operating system
thinks it is a normal user not an attacker.
- It could be possible that firewall will detect the malware. This will require software patches (updating your Operating System version).
Most computer providers have released software patches to overcome these issues. Since these are hardware related, it means that the hardware is what needs to be improved. Software can help, but not fully.
Built-in Firewalls are updated along with the Operating System (OS), since Firewalls are human programmed, they need to know how malware activity behaves. So, if the most recent version of OS is running on you device, the likely hood that your Firewall will know that this malware is carrying out Meltdown or Spectre 'activity' is high. This is because they are now aware of how these vulnerabilities will act.
As for outgoing traffic, and in terms of Iptables, it is unlikely that you know which IP address is trying to access your data.
I would also like to emphasise, again: Software can help, but not fully.
Hope it is clear now.
End of UPDATE
Kocher, Paul, et al. "Spectre Attacks: Exploiting Speculative Execution." arXiv preprint arXiv:1801.01203 (2018).
Meltdown and Spectre. (2018). Meltdownattack.com. Retrieved 1 April 2018, from https://meltdownattack.com/#faq-fix