Satarrans have the ability to look like other humanoids. Whether this is a natural ability or some kind of technology is unknown. They are resistant to phaser stuns: it took several hits to incapacitate their agent, "MacDuff".
The Satarrans have technology comparable to the Lysians, which is known to be far behind that of the Federation in most fields, most notably weapon and shield technologies.
Oddly, the Satarrans (and possibly the Lysians) had access to extremely advanced computer and neuroscience technologies which they used to selectively erase the memories of both the USS Enterprise's computers and the ship's crew. Since being so far ahead of the Federation in these two fields while so far behind in many others is implausible, some have hypothesized that "MacDuff" employed advanced alien technology that he acquired somewhere for his ruse instead of Satarran technology.
The Satarrans are a negligible threat. Despite their ability to alter memories, they have no tactical sense. When "MacDuff" altered the memories of the computer and crew of the Enterprise, he could have made himself Captain so he could carry out the mission, but instead he made himself "Executive Officer". Consequently, he was not in a position to simply order the crew to attack and destroy the Lysians, and he was defeated when he attempted to usurp Picard's authority.