  Recently, Large Language Models (LLMs) have made significant advancements and
are now widely used across various domains. Unfortunately, there has been a
rising concern that LLMs can be misused to generate harmful or malicious
content. Though a line of research has focused on aligning LLMs with human
values and preventing them from producing inappropriate content, such
alignments are usually vulnerable and can be bypassed by alignment-breaking
attacks via adversarially optimized or handcrafted jailbreaking prompts. In
this work, we introduce a Robustly Aligned LLM (RA-LLM) to defend against
potential alignment-breaking attacks. RA-LLM can be directly constructed upon
an existing aligned LLM with a robust alignment checking function, without
requiring any expensive retraining or fine-tuning process of the original LLM.
Furthermore, we also provide a theoretical analysis for RA-LLM to verify its
effectiveness in defending against alignment-breaking attacks. Through
real-world experiments on open-source large language models, we demonstrate
that RA-LLM can successfully defend against both state-of-the-art adversarial
prompts and popular handcrafted jailbreaking prompts by reducing their attack
success rates from nearly 100% to around 10% or less.
