Bishop Gray (Introd. to O. T. p.613) seems, as he often does, to hit the mark, as nearly as we can tell, when he deems it to be "by some Jew who invented the history, or collected its particulars from traditionary relations in praise of Daniel." This observation is little more than paraphrased by J. H. Blunt, when he writes (in loc.) "probably inserted into LXX from some ancient Jewish authority." The variations of text certainly suggest an oral tradition, perhaps even more strongly than in Bel and the Dragon.
Bissell says that Susanna "contains nothing which might not have come from the pen of a Hellenist" (p.445); and Westcott sees in this and other additions "the hand of an Alexandrian writer" (Smith's D. B. ed.2 I.714a), but thinks it not unlikely that he worked up earlier traditions. Certainly v.22 seems to shew that the author of the Greek of Th was evidently acquainted with the LXX of II. Sam. xxiv.14. "Wer die Susanna (in Walton's Polygl.4) nach Theodot. frei bersetzt hat," says Nestle, "wissen wir nicht" ( Urtext und übersetz.236).
It is noteworthy that Josephus shews no acquaintance with this or the other additions, though he makes some use of other uncanonical legends of Daniel (Jud. Ant. X.,10, 1; 11, 6 and 7). Schürer in Hauck's Encylop. (I.639), thinks Susanna and Bel and the Dragon may well originally have had independent existences. If so, this might help to explain Josephus' disregard of them.
It is a reasonable inference from v.57, that the author was a Jew in the strictest sense, and not from one of the ten tribes. Yet it should not escape notice that in v.48 "Israel" is apparently used for the entire people, including all the tribes.  The invidious contrast between the Israelitish and Jewish women is omitted in what Dr. Salmon calls, "the second Syriac recension" of Susanna, termed erroneously at one time "the Harklensian" (Speaker's Comm., p. xlvi.). The contrast in v.56 between Israel and Canaan is made into a stinging reproach, but is hardly to be understood literally as to the Elder's family descent.
J. Kennedy in Daniel from a Christian standpoint (p.55), says of this and the other Additions that there is "no means of determining when, where, or by whom written." He adds (p.56), "those who conceived and wrote the additions were both intellectually and spiritually incapable of appreciating the book [of Daniel] and its contents," and he concludes that they "belong to different ages and to entirely different conditions of thought." This estimate is a much too severe one, and very different from the opinion formed by some other equally qualified judges. The fear lest a favourable opinion of the quality of these pieces should lend any countenance to the Tridentine decree as to the Apocrypha, or seem to weaken the Protestant position with regard to them, appears to have operated, consciously or unconsciously, in shaping the views on this subject expressed by such writers. Probably acting under similar sentiments Ludovicus Cappellus, 1658 (quoted by Ball, 325a), calls the author "a trifler" (nugator), and styles his production "fabula ineptissima."
Jerome, in the Prologue to his Commentary on Daniel, says that Eusebius and Apollinarius replied to Porphyry's objection to these additions that "Susannae Belisque ac Draconis fabulas non contineri in Hebraico, sed partem esse prophetæ Abacuc filii Jesu de tribu Levi;" and apparently acquiesces in this statement. As there appears to be no other authority for attributing Susanna to Habakkuk, it is a question whether the LXX title to Bel and the Dragon was not applied to Susanna also "per incuriam." A. Scholz escapes the difficulty of Habakkuk both here and in Bel and the Dragon by regarding it as a merely symbolic title, which he renders by "Kämpfe" on very slender grounds (Esther und Susanna, Würzburg, 1892, p.138; and Judith und Bel und der Drache, 1896, p.204).
It must not be forgotten, however, that the authorship of Daniel is of course suggested by most of those who defend the canonicity of the book. Origen in his Epistle to Africanus maintains the solidarity of the piece with the book of Daniel. And it should be remembered, as a point of some strength, that Julius Africanus' correspondence with Origen at the beginning of century III., is the first record we have of any dispute as to its genuineness.
Professor Rothstein, in Kautzsch (I.172) gives very decidedly a contrary opinion, stating that Susanna and Bel and the Dragon, "haben mit dem Danielbuche nur insofern zu thun, als in ihnen Daniel eine Rolle spielt." But it is hard to offer conclusive proof that Susanna and Bel and the Dragon differ greatly in character from the independent historical "scenes" of which the first six chapters of Daniel consist; each, in nearly all respects, being intelligible when standing alone. It is hard also to shew that their incorporation, and constant acceptance, with the LXX was a deplorable mistake. And this difficulty is enhanced when we see that, so far as is known, all the Greek and Latin speaking Christians before Julius Africanus, and most of them after, fell unquestionably into what, if Rothstein and those who think with him are right, must be deemed a grave error. But even if it could be proved that these pieces were by the author of Daniel, the recent questions as to who that writer may have been, still further complicate the at present insoluble problem of the authorship of Susanna.
 If not, as Bissell in his note elegantly puts it, "it would be a bungling lapsus pennæ."