The Rambam rules that preserving human life overrides Shabbat entirely, and that one who hesitates to act quickly for pikuach nefesh commits a sin. This principle is foundational for any discussion of emergency cyber-defense operations on Shabbat.
דְחוּיָה הִיא שַׁבָּת אֵצֶל סַכָּנַת נְפָשׁוֹת כִּשְׁאָר כָּל הַמִּצְוֹת. לְפִיכָךְ חוֹלֶה שֶׁיֵּשׁ בּוֹ סַכָּנָה עוֹשִׂין לוֹ כָּל צְרָכָיו בְּשַׁבָּת עַל פִּי רוֹפֵא אֻמָּן שֶׁל אוֹתוֹ מָקוֹם. סָפֵק שֶׁהוּא צָרִיךְ לְחַלֵּל עָלָיו אֶת הַשַּׁבָּת סָפֵק שֶׁאֵינוֹ צָרִיךְ. וְכֵן אִם אָמַר רוֹפֵא לְחַלֵּל עָלָיו אֶת הַשַּׁבָּת וְרוֹפֵא אַחֵר אוֹמֵר אֵינוֹ צָרִיךְ מְחַלְּלִין עָלָיו אֶת הַשַּׁבָּת שֶׁסְּפֵק נְפָשׁוֹת דּוֹחֶה אֶת הַשַּׁבָּת: אֲמָדוּהוּ בְּיוֹם הַשַּׁבָּת שֶׁהוּא צָרִיךְ לְכָךְ וְכָךְ לִשְׁמוֹנָה יָמִים אֵין אוֹמְרִים נַמְתִּין עַד הָעֶרֶב כְּדֵי שֶׁלֹּא לְחַלֵּל עָלָיו שְׁתֵּי שַׁבָּתוֹת אֶלָּא מַתְחִילִין מֵהַיּוֹם שֶׁהוּא שַׁבָּת וּמְחַלְּלִין עָלָיו אֲפִלּוּ מֵאָה שַׁבָּתוֹת כָּל זְמַן שֶׁהוּא צָרִיךְ וְיֵשׁ בּוֹ סַכָּנָה אוֹ סְפֵק סַכָּנָה מְחַלְּלִין. וּמַדְלִיקִין לוֹ אֶת הַנֵּר וּמְכַבִּין מִלְּפָנָיו אֶת הַנֵּר וְשׁוֹחֲטִין לוֹ וְאוֹפִין וּמְבַשְּׁלִין וּמְחִמִּין לוֹ חַמִּין בֵּין לְהַשְׁקוֹתוֹ בֵּין לִרְחִיצַת גּוּפוֹ. כְּלָלוֹ שֶׁל דָּבָר שַׁבָּת לְגַבֵּי חוֹלֶה שֶׁיֵּשׁ בּוֹ סַכָּנָה הֲרֵי הוּא כְּחל לְכָל הַדְּבָרִים שֶׁהוּא צָרִיךְ לָהֶן: כְּשֶׁעוֹשִׂים דְּבָרִים הָאֵלּוּ אֵין עוֹשִׂין אוֹתָן לֹא עַל יְדֵי נָכְרִים וְלֹא עַל יְדֵי קְטַנִּים וְלֹא עַל יְדֵי עֲבָדִים וְלֹא עַל יְדֵי נָשִׁים כְּדֵי שֶׁלֹּא תְּהֵא שַׁבָּת קַלָּה בְּעֵינֵיהֶם. אֶלָּא עַל יְדֵי גְּדוֹלֵי יִשְׂרָאֵל וְחַכְמֵיהֶם. וְאָסוּר לְהִתְמַהְמֵהַּ בְּחִלּוּל שַׁבָּת לְחוֹלֶה שֶׁיֵּשׁ בּוֹ סַכָּנָה שֶׁנֶּאֱמַר (ויקרא יח ה) "אֲשֶׁר יַעֲשֶׂה אוֹתָם הָאָדָם וָחַי בָּהֶם" וְלֹא שֶׁיָּמוּת בָּהֶם. הָא לָמַדְתָּ שֶׁאֵין מִשְׁפְּטֵי הַתּוֹרָה נְקָמָה בָּעוֹלָם אֶלָּא רַחֲמִים וְחֶסֶד וְשָׁלוֹם בָּעוֹלָם. וְאִלּוּ הָאֶפִּיקוֹרוֹסִים שֶׁאוֹמְרִים שֶׁזֶּה חִלּוּל שַׁבָּת וְאָסוּר עֲלֵיהֶן הַכָּתוּב אוֹמֵר (יחזקאל כ כה) "גַּם אֲנִי נָתַתִּי לָהֶם חֻקִּים לֹא טוֹבִים וּמִשְׁפָּטִים לֹא יִחְיוּ בָּהֶם":
The [laws of] the Sabbath are suspended in the face of a danger to life, as are [the obligations of] the other mitzvot. Therefore, we may perform - according to the directives of a professional physician of that locale - everything that is necessary for the benefit of a sick person whose life is in danger. When there is a doubt whether or not the Sabbath laws must be violated on a person's behalf, one should violate the Sabbath laws on his behalf, for the Sabbath laws are suspended even when there is merely a question of danger to a person's life. [The same principles apply] when one physician says the Sabbath laws should be violated on a person's behalf and another physician states that this is not necessary. [The following laws apply when physicians] determine on the Sabbath that a person needs [a treatment to be administered] for eight days. We do not say that we should wait until the evening so that it will not be necessary to violate two Sabbaths on his behalf. Instead, the treatment is begun immediately, on the Sabbath, and even one hundred Sabbaths may be violated on his behalf. As long as a person is dangerously [ill] - or even if there is a question whether or not he is dangerously [ill] - and requires treatment, [the Sabbath] should be violated [on his behalf]. A lamp may be lit on his behalf and extinguished on his behalf. [Animals] may be slaughtered on his behalf, [food] baked and cooked on his behalf, and water heated for him, whether to drink or to use for bathing. The general principle for a person who is dangerously ill is that the Sabbath should be considered as a weekday regarding all his needs. When such treatment is administered, it should not be administered by gentiles, by children, by servants, or by women, so that they will not view the Sabbath flippantly. Instead, the treatment should be administered by the leaders of Israel and the wise. It is forbidden to hesitate before transgressing the Sabbath [laws] on behalf of a person who is dangerously ill, as [reflected in the interpretation in the phrase of Leviticus 18:5,] "which a person shall perform to live through them," as "['to live through them'] and not to die through them." This teaches that the judgments of the Torah do not [bring] vengeance to the world, but rather bring mercy, kindness, and peace to the world. Concerning those non-believers who say that [administering such treatment] constitutes a violation of the Sabbath and is forbidden, one may apply the verse [Ezekiel 20:25]: "[As punishment,] I gave them harmful laws and judgments through which they cannot live."